The First Annual Frontiers in Life Sciences Conference

IRIDESCENCE More than Meets the Eye

February 6 - 9, 2008Arizona State University - School Of Life Sciences

Old Main, Carson Ballroom, Tempe Campus

photo credit: Melissa Meadows

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Daily Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Fashion Show . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11

Guest Speaker Biographies . . . . . . . . . . . . . . . . . . . . . .12-15

Conference organizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Oral Presentation Abstracts . . . . . . . . . . . . . . . . . . . . . .16-35

Poster Abstracts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35-43

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44-45

TABLE OF CONTENTS

photo credit: Tomatito26 | Dreamstime Stock Photos

2

CONFERENCEOVERVIEW

3

A unique, integrative 4–day conference on iridescent colors in nature, Iridescence: More than Meets the Eye is a graduate student proposed and organized conference supported by the Frontiers in Life Sciences program in Arizona State University’s School of Life Sciences . This conference intends to connect diverse groups of researchers to catalyze synthetic cross– disciplinary discussions regarding iridescent coloration in nature, identify new avenues of research, and explore the potential for these stunning natural phenomena to provide novel insights in fields as divergent as materials science, sexual selection and primary science education . We invite you to join us for this exciting event February 6 – 9, 2008 at Old Main, Carson Ballroom, Tempe Campus .

Each day of the conference will be dedicated to a specific area of study . We have invited twelve main speakers from all over the world and from disciplines ranging from biology to nanotechnology . The day will begin with a series of plenary–style talks by invited speakers, followed by shorter talks by other participants as time allows . Afternoon break–out sessions centered on the day’s topic will give interested participants a chance to discuss and share ideas, leading to new collaborations and several publications . We will also have an evening poster session on Thursday February 7 . On the final evening, we will host a banquet and iridescent art event in collaboration with ASU’s Herberger College of the Arts and the Phoenix Art Museum . Please see the links below for more information about our invited speakers, daily themes and activities, and the final banquet .

4

IRIDESCENCE

“Iridescence: More Than Meets the Eye” would not have been possible without the generous grant provided by the School of Life Sciences Research and Training Initiatives Committee as part of the new Frontiers in Life Sciences program . This innovative program, to our knowledge unique to Arizona State University, provides an annual award of $30,000 to a group of graduate students at the School of Life Sciences to initiate and organize a conference or workshop . Frontiers in Life Sciences (FiLS) seeks to “highlight cutting-edge issues and discoveries in the life sciences” and “call attention to the excellent life science research going on in SoLS, publicizing our work both within and beyond ASU .” Proposals are accepted annually by the RTI committee, and are evaluated based on many criteria, including the intellectual scope and novelty of the meeting theme, an interdisciplinary emphasis, and a solid logistical and financial plan . As the first group at ASU awarded this grant, we hope that our attempt to call together some of the best minds in the world to explore the phenomenon of iridescence from a variety of viewpoints will make the RTI committee proud, and will be a great beginning for the Frontiers in Life Sciences program . For their valuable comments on our proposal, their help with advertising the event, and of course for trusting our group to be the FiLS “guinea pigs,” we would like to extend our deepest gratitude to the 2006-2007 RTI committee: James Elser, Andrew Hamilton, Yung Chang, Stan Faeth, Shelley Haydel, Josie Clark-Curtiss, Pierre Deviche, Rebecca Clark, Russ LaBrutto, and Peggy Coulombe .

We would like to thank our invited speakers, without whom we may not have received this grant or attracted so many other scientists from across the globe! Dr . Stephanie Doucet, Dr . Helen Ghiradella, Dr . Roger Hanlon, Dr . Darrell Kemp, Dr . Kevin McGraw, Dr . Daniel Osorio, Dr . Richard Prum, Dr . Ronald Rutowski, Dr . Matthew Shawkey, Dr . Mohan Srinivasarao, Dr . Doekele Stavenga, and Dr . Peter Vukusic have

already written letters of support for our grant proposal, allowed us to use their well-known faces and impressive biographies as advertisement on our website, and have worked closely with us throughout the planning of this conference . Additionally, they are each giving a 30 minute talk, helping to lead discussion sessions in the afternoons, and serving as judges for the student poster and talk competitions during the conference . We truly appreciate the support and enthusiasm that you have put towards this event .

We would like to say a special thank you to the artists and performers who have volunteered their time, resources, and talents to make our final banquet a memorable and unique event . Thanks to Galina Mihaleva, Jacqueline Benard, Dennita Sewell, Zak Jones, and to our models and other artists for your role in making this a truly interdisciplinary and entertaining conference .

ACKNOWLEDGEMENTS

5

ACKNOWLEDGEMENTS

6

Day 1 Mechanisms and MeasurementIridescent colors present a special problem for spectral quantification, as even slight movements of the colored object, illuminating light source and/or light collector can have large effects on the perceived spectra of the object . Despite this, many if not most researchers, particularly in the fields of animal behavior and evolutionary biology, have continued to use quantification methods that do not acknowledge this feature of iridescent coloration . While it is difficult to assess how detrimental this has been to the integrity of the results reported, there is a clear need for well–reasoned methodological recommendations that take in to account the interests and knowledge of both evolutionary biologists and physicists . How do we best characterize iridescent colors using modern spectrophotometric methods? Can we suggest ways of measuring these colors that

are feasible in both laboratory and field settings? How do these recommendations change for animals living under water? Can spectral characteristics help us to infer underlying optical mechanisms? What behavioral data are needed to decide on the best arrangement of object, light source and collector? These questions and more will be addressed by invited speakers and will be discussed in an afternoon break–out session .

Day 2 DevelopmentAnimals produce iridescent colors using highly ordered arrays of nanostructures . Next to nothing is known about how these nanostructural arrays are developed in vivo . How are these precise arrays produced during development? What cellular and/or genetic processes are involved? How do they respond to environmental perturbations? Can we gain insights or suggest promising directions by looking at modern nanofabrication methods or known principles of material self–assembly? Would studies of biological “nanofabrication” inform the growing field of nanotechnology?

Day 3 EvolutionLike sequins on a stage costume, iridescent colors seem ideally suited to highlighting behavioral movements or impressing potential mates . Indeed,

DAILY EVENTS

7

recent research efforts have provided support for the idea that iridescent colors may serve as indicators of male quality and may accentuate specific behaviors during courtship . However, the literature on this subject is still relatively shallow . Even less well studied is the role of iridescent colors in other evolutionary contexts . For example, iridescent colors may be used to produce startling and confusing flashes to ward off predation attempts, as efficient warning colors for aposematic species, or as a signal during aggressive interactions . In some intriguing cases, these colors may even function in animal crypsis . This perhaps unexpectedly wide range of biological function exhibited by iridescent colors makes questions regarding how and why they have evolved all the more compelling .

Day 4 EducationWe suggest that iridescent colors can serve as engaging examples for teaching students about a diverse set of often cross–disciplinary subjects such as optics, nanofabrication, animal behavior and the evolution of complex traits . Can we identify specific examples of iridescence well suited to classroom instruction? How might we harness the eye–catching power of iridescent colors in the science classroom? Can we introduce students to the growing field of nanotechnology by using biological examples of nanostructures? We have invited education experts, science administrators, and local teachers from a variety of disciplines to join us in constructing classroom recommendations and curricular initiatives related to iridescent colors . We will request the input of all participants, especially invited speakers, as we brainstorm creative ways of using iridescence in public education .

Final BanquetAs a final capstone event, we will host an evening banquet and art event on February 9 showcasing several local artists from ASU’s Herberger College

of the Arts and the Phoenix Art Museum . At this event, student dancers choreographed by Shouze Ma will wear iridescent costumes created by costume artists Galina Mihaleva and Jacqueline Benard in a fashion show-type performance . Following this, Dennita Sewell, Phoenix Art Museum curator of fashion design will give a lecture on the use of iridescence in traditional and modern day fashion and costume . We will also announce the winner(s) of the student poster competition and make final remarks . Registration for the conference is required to attend this event . The cost is $35, payable by check or cash at the conference registration table on February 6 . Please see the Registration page for details about reservations .

8

9

FASHIONSHOW

10

11

12

Stephanie Doucet is an Assistant Professor of Biological Sciences at the University of Windsor studying avian behavioral and evolutionary ecology .

Dr. Helen Ghiradella was born, raised, and educated in New York City . She received her BA (biology major and languages minor) from City College of New York, MA with John Anderson in Invertebrate Zoology at Cornell University, and PhD with James Case in Neurobiology at the University of California at Santa Barbara . After postdoctoral study with Kenneth David Roeder at Tufts University, she moved to Albany . From initial studies in insect hearing and firefly flash control, her research interests have gradually migrated closer to questions of biological pattern formation and development and, with the help of friends in engineering and physics, biological materials .

Dr. Roger Hanlon holds B .S ., MSc and PhD degrees in Biology and Marine Sciences and did postdoctoral work at Cambridge University . He moved to the Marine Biological Laboratory at Woods Hole in 1995 after 20 years at the University of Texas Medical Branch (Professor and Division Chief in the Marine Biomedical Institute) . His research focuses on adaptive coloration and behavior in cephalopods (squid, cuttlefish, octopus) . Overall, 130 peer–reviewed scientific papers have been published on these and related subjects . Structural coloration

is a major feature of cephalopod skin patterns used for communication and camouflage . The Hanlon lab has discovered physiologically active iridophores and we has recently used spectrometers to accurately quantify light reflection from intact skin, and begun to relate light reflection to ultrastructure .

Dr. Darrell Kemp completed his PhD in 2002 and is presently an Australian Research Council postdoctoral fellow, situated at James Cook University in tropical northern Australia . His is broadly interested in evolution and sexual selection, and his research focuses on the evolution of male mating strategies and exaggerated sexual traits . He uses field observation, experimental manipulation and quantitative genetics to test specific theoretical predictions using model biological systems, particularly insects . His most recent research has sought to understand the adaptive signaling significance of exaggerated iridescent male coloration in tropical butterflies .

Dr. Kevin McGraw’s research program centers on the control and function of striking colors in birds, including both pigmentary and structural forms . He and his students conduct multi-disciplinary investigations of the honesty-reinforcing mechanisms for avian color signals (i .e . diet, health, hormones) and the linked sexual or social function served by such colors (i .e . mate choice, status signaling) . Their work has concentrated mostly on

GUESTSPEAKERS

13

color control and communication in songbirds (especially finches and sparrows), but they have recently expanded their studies to parrots, penguins, ducks, and hummingbirds to understand how the mechanisms and functions of their diverse colors compare to those of well-studied passerine ornaments . One of Kevin’s main objectives at this conference is to encourage thought and discussion about whether or not iridescent coloration is biologically “special” and the extent to which we should make unique ecological, evolutionary, molecular, and physiological predictions about iridescent coloration compared to other types of color signals . Kevin is the faculty advisor of conference organizers Mike Butler, Lisa Taylor, Matthew Toomey, and Melissa Meadows .

Dr. Daniel Osorio works at the University of Sussex where he studies vision and visual behaviour of animals including primates, birds and cephalopods . His earliest research work was with Mike Land on the role of structural colour in butterfly tapeta . More recently he has

been interested in the properties of structural colors in bird plumage, and their meaning as signals . These colors range from simple hues to brilliant iridescence, but they have found that optically feathers are quite simple; they behave as more or less directional interference reflectors, and can be characterised by a small number of spectral measurements taken with a purpose–built goniometer .

Dr. Richard Prum is the William Robertson Coe Professor of Ornithology, Ecology and Evolutionary Biology at Yale University .

Dr. Ronald Rutowski has worked for over 30 years on both proximate and evolutionary aspects of mating behavior, vision, and visual signals in butterflies . Recent work in his lab has focused most intensely on iridescent coloration in butterflies, the mechanisms that produce such coloration, and the consequences of iridescence for its use as a signal in intra– and interspecific

photo credit: Ton Rulkens

photo credit: Tony Hisgett

14

15

interactions . He is a professor at Arizona State University, and is the faculty advisor of Nathan Morehouse, one of the conference organizers .

Dr. Matthew Shawkey completed his Ph .D . in Geoff Hill’s lab in 2005, is currently a post-doc in Steve Beissinger’s lab and will begin work as an assistant professor of integrative biology at the University of Akron in Spring 2008 . He is broadly interested in the mechanics, development and evolution of structural (both iridescent and non-iridescent) plumage color . Most of his work focuses on the two- and three-dimensional morphological basis of intra-and inter-specific variation in structural plumage color and the broad-scale evolution of structurally colored tissues .

Dr. Mohan Srinivasarao works at the School of Polymer Textile and Fiber Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology .

Doekele Stavenga studies Experimental Physics at the University of Groningen, the Netherlands, where he has been a professor of Biophysics since 1991 . Most of his research concerns the optics and physiology of insect eyes, but he has specifically focused on the spectral properties of butterfly vision . Recently his research has expanded to the optics of insect wings, especially butterflies . This entails analysis of the structure and reflectance spectra of single butterfly scales as well as the effect of scale stacks on the wing . He is furthermore interested in unraveling the interplay between insect colors and their color vision systems .

Dr. Peter Vukusic is a physicist leading the work on natural photonics at the University of Exeter .

photo credit (right corner clockwise: User:maxo, Benjamint444, Bob Peterson, Tony Hisgett, Bob Peterson, Bob Peterson

16

CONFERENCEORGANIZERS

Mike Butler (mike .butler@asu .edu) received his bachelor’s degrees in biology and physics from Bowdoin College and his master’s degree in raptor biology from Boise State University . He is now in his second year in a doctoral program at Arizona State University under Dr . Kevin McGraw . Currently, his research focuses on immune function, carotenoid allocation, and coloration of mallard ducks during post–natal development .

Melissa Meadows (melissa .meadows@asu .edu) holds a B .S . in Marine Biology from the University of North Carolina at Wilmington, but has since turned her attention to iridescent bird coloration . She is studying iridescent coloration as an honest signal of quality in aggressive interactions and mate–choice, and is particularly interested in the information content that such signals may convey . She is taking advantage of Arizona State University’s large population of Anna’s hummingbirds, whose gorget feathers are pictured above, for this work . Melissa is beginning her third year as a doctoral student at ASU, and is advised by Dr . Kevin McGraw .

Nathan Morehouse (nmorehouse@asu .edu) received a B .S . in Biological Sciences from Cornell University and is currently a doctoral candidate working with Dr . Ron Rutowski . He is interested interested in the selective pressures and nutrient dynamics underlying the evolution of bright coloration in animals . His work currently focuses on

the importance of nitrogen limitation and female mate choice to the evolution of sexually dimorphic wing coloration in the Cabbage White butterfly, Pieris rapae . He is also interested in the diversity of optical mechanisms employed by animals to generate bright color patterns .

Lisa Taylor (lisa .a .taylor@asu .edu) studies sexual selection and coloration in Habronattus jumping spiders . Males of this genus are often highly ornamented with bright (sometimes iridescent) colors which they display for females in elaborate courtship dances . The goal of her research is to understand how variation in male color affects female choice, and ultimately, what a male’s colors might tell a female about his quality as a mate .

Matthew Toomey (matthew .toomey@asu .edu) is a graduate of the University of Vermont and is currently pursuing a Ph .D . at Arizona State University . His research is focused on the role of carotenoids in color vision and the evolution of colorful plumage in birds . Matt is beginning his third year with advisor Dr . Kevin McGraw .

17

18

ORAL PRESENTATION

ABSTRACTSAge-Related Differences in the Iridescent Plumage of Male Tree Swallows: Hue and Brightness Signal Different Aspects of Individual QualityPierre-Paul Bitton± and Russell D . Dawson, University of Northern British Columbia, Prince George, British Columbia, Canada, bittonp@unbc .ca

Age-related differences in plumage characteristics of birds have been relatively well researched in carotenoid- and melanin-based coloration but not for structurally colored feathers . In this study, we investigated age-class related differences in plumage attributes of male tree swallows (Tachycineta bicolor) which possess metallic green to metallic blue iridescent plumage on their dorsal surface . Our results showed that, at the population level, older males were brighter and reflected light maximally at shorter wavelengths (i .e . were bluer) . Differences in plumage brightness were most likely caused by changes within individuals as males increased in brightness between the first time they were captured and the subsequent year . Differences in hue, however, were not due to within individual changes, but rather appear to be

the result of greener individuals having lower survival and/or nest site fidelity . Indeed, relatively dull, greener birds had a lower probability of being recaptured the subsequent year . In contrast, we found that if birds captured in their first year as breeding adults were relatively bright, color did not seem to influence subsequent recapture probability . These results suggest that plumage attributes in male tree swallows have the potential of being honest signals of quality . Furthermore, plumage brightness and plumage hue might signal different aspects of male quality in this species .

Iridescent Eyespots and Sexual Signaling in Peacocks Roslyn Dakin ±, Department of Biology, Queen’s University, Kingston, Ontario, Canada, dakinr@biology .queensu .ca

The glittering plumage of the peacock is one of nature’s most dazzling displays . Previously, it has been shown that peahens prefer to mate with males that have longer trains with a greater number of iridescent eyespots . More recent studies of captive peafowl indicate that the complex structural colouration of these eyespots might be important

in mate choice independently of train morphology . I am addressing questions about the function of eyespot colouration in several ways . First, I am testing the hypothesis that peahens assess eyespot colour using an experimental approach in which I modify the eyespot signal . Second, I am testing the possible signal content of the iridescent plumage . To this end, I am examining relationships between measures of individual condition and eyespot colour to test the hypothesis that the iridescent colour is an honest signal of genetic quality . I am also looking at the nanostructural basis of the eyespot colour to test whether individual differences in nanostructure are responsible for the observed variation in colour and in degree of iridescence, which would suggest that the eyespots signal information about the individual during the process of feather growth . Finally, I describe the ways that peacocks exploit the directionality of their eyespot signals during display . My results so far indicate that peacocks are able to optimize their signaling effort by orienting their trains towards the sun, for maximum eyespot reflectance towards female targets, and that peacocks may use their display dances to manipulate females to view them from the best angle .

19

The Function of Iridescent Coloration in Birds: Insights From Multiple Species Stephanie Doucet*, Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada, sdoucet@uwindsor .ca

To date, research on the function of iridescence in birds has focused on its potential role in mate choice . In particular, several studies have assessed the hypothesis that iridescent plumage coloration might serve as an honest indicator of male quality . While this hypothesis is gaining increasing support, further research is needed before any generalizations can be made . Moreover, other possible hypotheses for the function of iridescent plumage remain virtually unexplored . Here, I use data from four species to evaluate the possible role of iridescence in honest signaling, species recognition, mutual mate choice, and defense against

predators . These field investigations and experimental manipulations involving satin bowerbirds, wild turkeys, royal f lycatchers, and mallards demonstrate the importance of iridescent signaling across distantly-related taxa . Together with other studies, these data suggest that multiple selective forces have favored the evolution of iridescent plumage coloration in birds .

Development of Iridescent Butterfly Scales: How to Make a Photonic Crystal...Or Two Helen Ghiradella*, Department of Biology, State University of New York, Albany, New York, hghff@albany .edu

Biological organisms use a limited set of materials to produce an astonishing variety of complex non-living structures . Moreover, they may be doing this with a

corresponding economy of information, for it seems that the same developmental processes may get reworked to support vastly different functions in different places and in different organisms . To illustrate this I will begin with a brief overview of what is known about development of unspecialized and of iridescent lepidopteran scales . I will then consider whether homologs of this “developmental architecture” may form the underpinnings of other systems as diverse as the insect tracheal system, the auditory sensilla of noctuids and other moths, the machinery that coordinates the contraction of skeletal muscle fibrils in response to the motor nerve impulse, and the bioluminescent “crystalloids” in the scales of polynoid scaleworms . If so, we may hope that understanding of any of these will yield insights into the structure and development of the others . . .and more .

20

Far Field Scattering Pattern of Differently Structured Single Butterfly ScalesMarco A. Giraldo ±1, Shinya Yoshioka2, and Doekele G . Stavenga1, 1Department of Neorobiophysics, University of Groningen, The Netherlands, 2Graduate School of Frontier Biosciences, Osaka University, Japan, m .a .giraldo@rug .nl

The wing scales of pierid butterflies are studded with beads, whose role in the generation of color is twofold . First, they scatter light incoherently, proportionally to the density of beads and, second, they store pigment that absorbs light in a restricted wavelength range . We studied six species of butterflies . The angular reflectances of single scales were measured and compared with their anatomy . Light scattered by beaded scales of Pierids follows Lambert’s cosine law . Multilayered scales of Morphos, however, scatter light anisotropically . They show a characteristic linear pattern that is perpendicular to the ridges . Scales of the silverspot butterfly, Dione juno, have an almost featureless upper surface . The windows, spaces limited by ridges and crossribs, are closed by unpigmented chitin layers that work as a mirror to incident light . A very interesting case is the purple tip butterfly, Colotis regina . The purple areas at the tip of the dorsal wings are composed by cover and ground scales . Ground scales have beads that selectively absorb light of short and medium wavelengths, causing the scattered light to be red . Cover scales are multilayered and beaded resulting in both diffuser- and morpho-like effects .

Dynamic Iridescence and Passive White Reflection: Their Uses in Signaling and Camouflage in CephalopodsRoger T. Hanlon*, Lydia Mathger, and Justin Marshall, Marine Biological Laboratory, Woods Hole, Massachusetts, rhanlon@mbl .edu

Cephalopods mollusks possess extravagant, changeable skin that is used in a wide variety of behavioral functions . Speed of change of skin patterns is on the order of <1 second for pigmented chromatophore organs, and 1-5 seconds for iridophores (structural reflectors) in vivo . Squids and cuttlefish produce conspicuous iridescence and bright whiteness during agonistic displays, some aspects of courtship, mate guarding, and predator escape . These will be explained and illustrated with underwater video . Whiteness is produced by physiologically passive leucophore cells lying subjacent to chromatophores and iridophores, and is only visible when overlying chromatophores are retracted . White spots and other signaling markings can be dynamically enhanced by expansion of adjacent dark chromatophores . Dynamic camouflage is also produced with the aid of multi-colored iridescence and whiteness, both of which complement the short-wavelength chromatophores . Sophisticated camouflage on a wide variety of visual backgrounds will be illustrated . Polarized light reflected from iridophores can be passed through the chromatophores, thus enabling the possible use of a hidden communication channel, because cephalopods can perceive polarized light .

Nanostructural and Fourier Analysis of Dermal Iridophores in Sceloporus Lizards with Evolutionary Variation in Blue Signaling PatchesDiana K Hews1, A . D . Leache2, M . D . Shawkey3,2, D . J . Barnes1, Indiana State University, Terre Haute, Indiana; 2University of California, Berkeley, California; 3University of Akron, Akron, Ohio, dhews@isugw .indstate .edu

We examined blue color production in Sceloporus lizard species that vary in occurrence of blue abdominal skin patches, an ancestral trait for the genus used in social signaling . Histological work (Quinn & Hews 2003) supports the hypothesis that white skin results when melanin underlying an iridophore layer is reduced; wavelengths not initially scattered by the iridophore layer are reflected by an underlying reflective collagen layer . Here, we assessed other potential mechanisms contributing to species differences in abdominal color, evaluating nanostructure of iridophores in TEMs in males of blue- and of white-bellied species . We tested the hypotheses that the species differed in guanine platelet: 1) thickness; 2) spacing (interplatelet gap); 3) orientation; or 4) number of layers (c .f . Morrison 1995) . Only mean platelet gap differed, and was significantly greater (P < 0 .047) in the white species . Individual variance in mean values (as assessed in 10 TEM transects per male) also did not differ significantly . Strengths of trait correlations differed between species; the white-bellied species (with evolutionary loss of blue color) had a larger number of weak correlations (r < 0 .5), consistent

21

with relaxed selection on iridphore features . Fourier analysis of TEMs revealed that iridophore platelets of both species were sufficiently organized and at the correct scale to produce color by coherent light scattering alone . Subsequent radial analyses incorporating estimated refractive indices of guanine and cytoplasm created predicted reflectance spectra that matched actual spectra in the blue species but not in the white, suggesting that melanin is essential for color production .

Seeing Is Believing: Using Color to Capture the Imagination of Students in the Classroom and Online Charles Kazilek, School of Life Sciences, Arizona State University

Reaching students and educators in the classroom has never been more important for the sciences . One of the best ways to engage students and teachers is visually and in particularly using color . The amazing color images from iridescence and florescent

objects are perfect tools for capturing the imagination of students and provide natural entry into many scientific topics . Two award winning web sites will be presented as examples of how color can be introduced online and into the classroom . Ask-a-Biologist and the Paper Project both have content on color designed for students and teachers in grades K-12 . Both sites are long-running and award winning examples of how to take basic science and imbed it into colorful classroom activities .

22

The Evolution of Structural Coloration in Butterflies: Sexual Selection, Sexual Dimorphism and Condition-DependenceDarrell J. Kemp*, School of Marine and Tropical Biology, James Cook University, Australia, email: darrell . kemp@jcu .edu .au

Models for the evolution of signals as honest indicators of mate quality predict that the expression of such signals should be costly and depend upon the condition of the bearer . Such condition-dependence is thought to evolve as a form of phenotypic plasticity, whereby individuals respond to their environment (e .g ., the amount of available resources) in order to optimize the trade-off between viability and reproduction . Because male sexual traits are more closely linked to reproductive success than non-sexual traits, they are predicted to display stronger condition-dependence . Furthermore, where analogous traits are seen in

females, theory predicts greater sex differences in the absolute degree of trait expression (i .e ., greater levels of sexual dimorphism) . In this talk I discuss these factors in relation to structural coloration, drawing upon recent empirical behavioral and quantitative genetic research in two model butterfly species, Colias eurytheme and Eurema hecabe .

Mechanisms of Iridescent Structural Color Production in Blue-Black Grassquit Feather Barbs Rafael Maia±, João Victor O . Caetano, Sônia Nair Báo, and Regina H . F . Macedo, Universidade de Brasília, Brazil, rafaelmaia@unb .br

Structural colors are produced through interference of differentially reflected wavelengths, and are a component of the visual communication system of many animal taxa . Bird plumage may produce iridescent colors due to the superposition of layers with different refractive index, such as keratin and melanin layers . Given the optical properties of these

refractive mediums and their nanostructural anatomy and organization, thin film modeling may be used to predict the light behavior and thus infer on what characteristics are important for color production, revealing the proximate mechanisms of visual signaling . We conducted transmission electron microscopy on the feather barbules of 10 male blue-black grassquits (Volatinia jacarina), which exhibit a UV-reflecting iridescent plumage, in order to characterize the nanostructural components involved in color production . From each barbule, we measured keratin cortex and outer melanin layer thickness, number of melanin granules in the melanin layer, and diameter of these granules (melanin layer thickness divided by the number of granules) . We found that blue-black grassquit barbules display a 138 .9 ± 19 .9 nm thick melanin cortex, followed by a 407 .7 ± 119 .6 nm melanin layer formed by 2 .4 ± 0 .3 melanin granules 172 .2 ± 37 .1nm in

23

diameter (all mean ± sd) . The model that best predicted the reflectance spectra considers only air/keratin and keratin/melanin interfaces, and the thickness of the keratin layer . These results are in accordance with the growing knowledge of structural color production by avian feathers, and indicate that the nanostructural characteristics of male blue-black grassquit barbules can account for its coloration characteristics .

Mechanisms of Cephalopod Structural Coloration: Field and Laboratory Data Lydia Mathger, Justin Marshall, and Roger Hanlon, Marine Biological Laboratory, Woods Hole, Massachusetts, lmathger@mbl .edu

Color change in cephalopods (squid, cuttlefish and octopus) is unrivaled in the animal kingdom . Their sophisticated skin containing pigmented chromatophore organs, structurally reflecting iridophores and light scattering leucophores gives these animals an ability to almost instantaneously change body patterns for camouflage and signaling, despite their apparent color-blindness . Here we present data on the structures that are involved in cephalopod color change: chromatophores, iridophores and leucophores . In the laboratory, we can measure the spectral reflectance of each of these structures and by varying the angle of observation and angle of incident illumination, we can make inferences regarding their optical mechanisms . Chromatophores do not produce color by structural coloration; they are pigmented organs that

act as filters to the underlying reflector cells . Iridophores act as multilayer reflectors, whereas leucophores appear to be perfect diffusers, appearing equally bright from all angles of view . Recent advances in technology have enabled us to take the spectrometer equipment underwater, enabling us to take measurements of cephalopods (Sepia apama, South Australia) in their natural habitats . We show that while the colors of certain body parts are well suited to match the colors of their surroundings, other body parts are conspicuous, suggesting involvement in visual signaling .

Interspecific Variation in Avian Iridescent Coloration: Ecological, Morphological, Phylogenetic, and Quality- Signaling Predictors Kevin J. McGraw*, School of Life Sciences, Arizona State University, Kevin .McGraw@asu .edu

Our understanding of both proximate and ultimate causes of variation in iridescent coloration in animals has improved dramatically in recent

decades, but, compared to mechanistic and functional lines of investigation, macroevolutionary comparative studies are lacking . Here I review taxonomic variation in the production and display of iridescent coloration in birds . First, I use published literature and meta-analytical techniques to test the prediction that avian iridescent colors are dependent upon the condition of individuals and thus could serve as honest advertisements . Second, I will track phylogenetic variability in iridescent coloration and examine dietary, life-history, and morphological (i .e . body location) predictors of interspecific variation in avian iridescence . These data will be compared to similar, recent studies of pigment-based (i .e . carotenoid, melanin) color ornaments in birds to evaluate the likelihood with which different selective pressures have acted on feather iridescence .

24

Diverse Color Production Mechanisms are Responsible for Convergent Blue Structural Coloration in a Butterfly Mimicry Complex Nathan I. Morehouse1, Marco A . Giraldo2, Ron L . Rutowski1 and Doekele G . Stavenga2, 1School of Life Sciences, Arizona State University, 2Department of Neurobiophysics, University of Groningen, The Netherlands

Examples of convergent evolution of animal coloration are commonplace, particularly in the study of mimicry, where visual cues have played a central role in our understanding of how and why mimicry evolves .

However, in many of the species studied thus far, the underlying color-producing mechanisms involved in color mimicry traits are similar if not identical . For instance, the color patterns of the classic Müllerian mimics the Monarch (Danaus plexippus) and the Viceroy (Limenitis archippus) are produced in both species by the deposition

of red ommochrome pigments and black melanin pigments within the wing scales . Here, we present a mimicry complex where one part of the aposematic color pattern is an iridescent blue produced via structural mechanisms: the Batesian mimicry complex surrounding the Pipevine Swallowtail, Battus philenor . While diffusely-reflecting color elements of this aposematic pattern are likely to be produced by pigments common to all species in the mimetic complex (e .g . melanins, ommochromes), the mechanisms producing blue coloration in models and mimics are uncertain given the diversity of known mechanisms that generate iridescent blue within the represented

butterfly taxa . Using transmission and scanning electron microscopy, spectrophotometry of intact wings and single wing scales, and mathematical modeling, we reveal at least three distinct optical mechanisms from five species in this mimicry complex that generate the blue component of the color signal . Our work thus reveals that the convergence in

iridescent blue coloration in this mimicry complex belies a striking diversity of underlying color production mechanisms .

Measurement and Meaning of Iridescence in Bird Plumage Daniel Osorio*, School of Life Sciences, University of Sussex, Brighton, United Kingdom, d .osorio@sussex .ac .uk

As colours flash from black to brilliant but changing hues, iridescence catches the eye by breaking the rules that govern commonplace materials, and this is why birds have iridescent courtship displays . Biologists ask if the purpose is simply to attract attention, or if iridescent plumage can transmit information about the qualities of a potential mate . To answer these questions we need measurements to describe the brilliance of a hummingbird or bird of paradise: how colours change as they move and how they may be seen in display . Iridescent plumage is remarkable for the purity of the colours, its blackness, and its directionality, but we can capture these properties with a few simple geometrical measurements of reflected light . Measurements imply near crystalline order in the nanostructure of black pigment and air embedded in feather protein, but they show that feathers work as tuned mirrors seems, which lack the 3-dimensional complexity of insect cuticles . To conclude I will compare the iridescence plumage of individuals within a species - the magnificent frigate bird - and ask how iridescent plumage might complement the colour, sounds and movement in their courtship .

25

Optimality of Triply Periodic Iridescent StructuresLeon Poladian, Maryanne C .J . Large, and Michelle Rigozzi, University of Sydney, Australia, leonp@maths .usyd .edu .au

At least five species of butterfly are now known to possess three dimensional periodic microstructures, however the specific geometry and topology of the microstructure remains ambiguous . Two of the several proposed structures are: the diamond (D) which is a four-fold coordinated structure on a face- centred cubic lattice; and the gyroid (G) which is a three-fold coordinated structure on a body-centred cubic lattice . In other organisms, a six-fold coordinated P structure on a simple cubic lattice has also been observed . Is it a coincidence that these three structures are the three most common and simplest triply periodic minimal surfaces (TPMS)? These structures and their lower dimensional coun-terparts show a striking resemblance to structural phases that appear in

complex fluids. Although, the specifics of the developmental mechanisms remain to be determined it is fruitful to explore to types of structures that minimise interfacial energy . Thus we used the Landau theory of phase transitions, to investigate the diversity of such structures . Phenomenological free energy functions and their corresponding phase diagrams are derived for transitions between structural phases previously unexplored with his method . This study is then complemented by an optical analys is of the stable structures found in the phase transition analysis . We perform a photonic

bandgap analysis on a variety of these iridescent structures and compare the degree of global and local iridescence and how it might vary with numerical aperture . We also explore the optimality of these structures as we vary the volume fraction of the solid and air phases .

Evolutionary Photonics: The Interface of Optics, Phylogenetics, Biochemistry, Development, and Behavior Richard O. Prum*, Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, Richard . prum@yale .edu

Photonic structures are classified according to whether they exhibit 1D, 2D, or 3D periodicity . These classifications have not considered whether nanoorder is on the scale of many scatterers or limited to local scales . Local order produces quasi-ordered materials that are common in biological systems and present new challenges for

26

physical analysis . Traditionally, biologists have accepted the standard optical classifications of the mechanism of color production, But these optical concepts are effected by the intellectual history of physics and the mathematics of analysis . The traditional optical classification creates problems for evolutionary analysis by obfuscating the fundamental physical commonalities shared among different coherently scattering anatomies . Comparative work on the evolution of structural colors in birds and butterflies document that many color producing nanostructures have evolved across the boundaries within the traditional optics tool box, defying the traditional notions of optical mechanism . With few exceptions,

we still know relatively little about the development of color producing nanostructures . There are two alternative mechanisms– self assembly and “cellular” assembly . Self assembly includes physical and biochemical processes in which the nanostructure results from the ordered interactions of the materials themselves . Cellular assembly include more complex physiological mechanisms of living cells . Examples of cellular mechanisms include butterfly wing scales, beetle cuticles, and likely keratin/melanosome arrays in iridescent feather barbules . TEM images of the development of the spongy medullary β-keratin in blue macaw bird feathers indicate that this material is a self assembled nanostructure . Future discussion of

the evolution of structurally colored anatomical systems should be informed by these systems are self assembled or cellularly assembled .

Photo-Real Rendering of Iridescence From Thin Films in InsectsMark J. Prusten, Silicon Arts, Tucson, Arizona, photondyn@silicon-art .com

Iridescence is found in terrestrial animals, and is most highly developed in two groups, insects and birds . Perhaps not coincidentally, these classes also exhibit well developed visual systems, and protean body coverings . In insects, such colors are often considered as anti-predator adaptations, either crypsis or aposematism, or a means of thermoregulation . This paper presents the modeling and development on High Dynamic Range Images, HDRI, Photo-real shaders for simulating the optical characteristics of the surfaces of both winged insects like butterflies and moths and non-winged insects such as beetles . The shader will simulate the thin film structure of the scales on butterflies . These Iridescent scales are visually stunning structures that reflect highly saturated color . They also create an array of non-chromatic optical phenomena, such as polarization, polarization mixing and highly directional flashes .

27

The influence of sub-surface scattering, global illumination, final gathering and spectral rendering and the influence of motion blur or movement created flashes will be presented for a variety of these insects . The simulation of the polarized light and the interaction of the insects with classic lighting setup will be reviewed were the illumination varies greatly in spectrum and intensity .

Measurement of Iridescent Signals Informed by Behavior and EcologyRonald Rutowski*, School of Life Sciences, Arizona State University, r .rutowski@asu .edu

A recurrent hypothesis about animal communication is that communicatory behavior and signals should be adapted to enhance reception of the signal by intended receivers . Because of their often highly

directional properties and the therefore restrictive set of geometries of light source, sender and receiver that allow for maximal transmission, iridescent colors present a special challenge when used as communicatory signals . Poulton (1890) was one of the first to point out this issue and proposed that iridescent signalers should behave in ways that enhance signal transmission . In particular, the expectation is that the behavior of the senders of iridescent signals will have evolved to enhance the perception of the signal in those behavioral and ecological circumstances in which it is typically or most likely to be displayed . There have been few efforts to test this expectation, but these considerations have important implications for how we measure and describe iridescent signals and their production and for inferring what might be the salient features of such signals . What are the relevant features of the ambient lighting for iridescent

signals? What aspects of sender behavior and the reflecting structures enhance signal perception by receivers? These and other issues will be discussed to provide a framework for thinking about how iridescent signals are described and measured in behaviorally and ecologically relevant ways .

A Physically Based Anisotropic Iridescence Model for Rendering Morpho Butterflies Photo-RealisticallyIman Sadeghi, University of California- San Diego, La Jolla, California, sadeghi@gmail .com

Rendering the brilliant iridescent colors of the Morpho butterflies has been a challenge in computer graphics . The cause of vivid blue color of the wings of these species is not as the result of the pigments of the wing . They are caused by the physical microscopic structures on the scales of the wing . These

28

micro-structures has been studied extensively in various fields by different expertise . Modeling these micro-structures on a computer, if not impossible, would require huge amount of data storage, computing power and complex access mechanisms . Therefore, rendering the appearance of these butterflies requires developing simplified, yet accurate, models which demonstrate the behavior of their micro-structures in different lighting conditions . In this paper I have addressed the problem of rendering the anisotropic iridescence colors of the Morpho butterflies photorealistically . The developed model is physically based and combines two previously presented

models; Multi-layer thin film model [Yinlong Sun . 2006] and separate lamellae model [S .KINOSHITA et al . 2002] . Both of those models fail to describe the anisotropic nature of the light reflectance on these structures . The introduced model in this paper produces an anisotropic model with interpolating between those two isotropic models . The model is based on the physical properties and analytical derivations of the microscopic structures of on the scales of the wings . Rendered images with this model match the experimental description [Fox 1976; Simon 1971] of iridescence properties of the Morpho butterflies .

Lack of Plumage Ultraviolet Status Signaling in Blueblack Grassquits (Volatinia Jacarina)Eduardo S. A. Santos±, Regina H . F . Macedo, Universidade de Brasília, Brazil, e .salves@gmail .com

Plumage patches that reflect ultraviolet (UV) coloration may be important signals in mate choice . However, few studies have tested if this function also occurs in male-male competition . In the blue-black grassquit (Volatinia jacarina), both the blue-black and white plumage coloration of males reflect UV . Previous studies have demonstrated that the blue- black coloration is associated with male body condition, and also, less

29

parasitized males present brighter reflectance . We tested the possibility that UV coloration of male plumage is associated with status signalling in competition for resources . We conducted experimental manipulations using an artificial food source to produce agonistic encounters among males, and took spectrophotometric measurements of the blue-black rump and wing coverts and white under-wing patch . Four indices were calculated to describe the variation in the blue-black and white coloration: brightness, as the sum of reflectance between 320 and 700 nm; hue, as the wavelength of maximum reflectance; intensity, as the maximum reflectance reached; and UV chroma, as the sum of reflectance between 320 and 400 nm, divided by the sum of reflectance between 320 and 700 nm . We found no significant effect of the measured indices of UV reflectance of the three color patches on the dominance of male blue-black grassquits . To date, there are very few studies reporting on the role of UV coloration in signalling within the context of male-male interactions . However, the first evidences seem to point

toward a smaller role of UV coloration in intra-sexual as compared to inter-sexual communication .

Iridescent and UV Wing Signals in a Tropical Helicopter Damselfly Tom D. Schultz1 and Ola M . Fincke2, 1Department of Biology, Denison University, Granville, Ohio, 2Department of Zoology, University of Oklahoma, Norman, Oklahoma, schultz@denison .edu

The tropical damselfly Megaloprepus caerulescens exhibits sexually dimorphic wing patterns that are l ikely play a role in courtship and territorial defense . Both sexes exhibit white and violet patches on the t ips of their transparent wings, but in reverse position . Translucent white patches are pigmentary, but the violet color of the non-transmissive bands arises from thin-layer interference and a stack of 12-14 epicuticular layers on either side of the wing plane . Both patches reflect wavelengths between 325 and 400 nm when the viewing angle is normal to the wing surface, however, the iridescence and UV reflectance of the dark patches are extinguished at angles of 45 degrees or less . With the changing wing angle during the stroke cycle these wing reflectors would provide a flashing UV signal that may be used to distinguish male from female damselflies .

From Flight to Bright – How Qualcomm’s Inspired by Nature Technology has Kept Mobile Phones Powered UpCheryl Schwarzman, Qualcomm, Inc . San Diego, California, cschwarz@qualcomm .com

mirasol ™ displays are a technology breakthrough that promise substantial performance benefits over competing display technologies . The reflective displays, based on Interferometric Modulation (IMOD) technology, require no backlighting

and can be viewed in bright sunlight and in a wide range of environments . Moreover, these displays offer a significant reduction in power consumption as compared to other display technologies, while extending device battery life and enabling new features . mirasol ™ displays work by reflecting light so that specific wavelengths interfere with each other to create pure, vivid colors . The phenomenon that makes a butterfly’s wings shimmer is the same process that gives mirasol displays their color . mirasol ™ displays will enable an optimum user experience for consumers who

photo credit Lisa Taylor

30

demand more from their wireless devices . Qualcomm MEMS Technologies, Inc . currently has locations in San Diego, California, San Jose, California, and Hsinchu, Taiwan .

Spectral Iridescence in Coleoptera: The Evolution and Function of Beetle Diffraction GratingsAinsley E. Seago±, University of California, Berkeley, California, seago@nature .berkeley .edu

Insect colors have long been classified into two categories: pigmentary and structural, with the latter most commonly exemplified by “iridescent” colors arising from multilayer thin-film reflectors . True spectral iridescence, which arises from diffraction gratings at the surface of the integument, has traditionally been considered a rarity among beetles . A survey of U .S . collections indicates that this structural color mechanism is in fact far more widespread than previously suspected; recent phylogenetic analyses of Coleoptera provide a conservative preliminary estimate of twelve independent origins of diffraction gratings in this order . Ecological and morphological

similarities between many iridescent taxa suggest that diffraction gratings fulfill one or more shared functions across multiple lineages of Coleoptera .

Levels of Organization as a Framework for Examining the Mechanics and Evolution of Bio-Optical TissuesMatthew Shawkey*, Department of Biology, University of Akron, Akron, Ohio, mshawkey@nature .berkeley .edu

Structures are composed of materials organized in from zero to three dimensions . Organization imparts properties to materials that they would not have otherwise; a structure made of given materials arranged in an unorganized way will have different properties than one made of the same materials arranged in an organized way . Similarly, the consistency of that organization will affect the structures’ properties; a one- dimensionally organized object will have different properties than a three dimensionally organized object . Colors of feathers can be created either by unorganized or organized tissues composed of keratin, air and pigments . Iridescent colors are created solely by organized

tissues while non-iridescent colors can be created by both organized and unorganized tissues . Evolutionary transitions between non-iridescent and iridescent colors in the grackles and allies (Family Icteridae) and in hummingbirds (Family Trochilidae) occur when tissues shift between unorganized and organized forms . However, the colors of these two groups are dramatically different . These differences are probably caused by phylogenetic and physiological constraints and the functions that these colors serve . Grackles lack the elongated and sometimes hollow melanin granules present in hummingbird feathers that may create brighter and more saturated iridescent colors . Wild turkeys Melleagris gallopavo and other species arrange similar hollow melanin granules in two dimensions to create bright iridescent color . Three dimensionally arranged structures, by contrast, may create non-iridescent color .

31

Electron tomography and three dimensional fourier data suggest th at non-iridescent “spongy” structural tissue is organized at the same spatial scale in all three dimensions . This consistency may explain why the colors created by it, unlike those created by one and two dimensionally organized tissues, do not change with angle of viewing . Interestingly, evolutionary transitions between 3D organized tissues and other organized tissues may be relatively rare . Levels of organization thus provide an excellent framework for examining mechanisms and evolution of bio-optical tissue .

Usefulness of Iridescence as a Learning Progression Theme Through K-12 Science EducationJan Snyder, National Science Foundation GK-12 Program Coordinator, Arizona State University

An important factor that leads to successful outcomes for science education is the ability to instill a sense of wonder in students . Students of all ages, ethnicities, and both genders, can be more readily hooked on science if they are able to develop a personal sense of wonder . With competition educators experience from ongoing

entertainment sources opportunities to foster student-based wonder is not readily accomplished . Moreover, the need to link state standards with every lesson means that educators must balance studentinterest with state-determined policy . Color provides a natural opportunity to incorporate these two issues such that science lessons can tap student interest and personal experience with state requirements meant to meet regulations now in force due to the N .C .L .B . Act . Students have seen rainbows, but so have they witnessed the iridescence associated with bird feathers, some fish in an aquarium (thought

32

not as common as with terrestrial systems), wings of butterflies, flies and beetles . The students’ familiarity with these phenomena can be readily associated with inquiry-based, and standards aligned, K-12 science lessons . Furthermore, the strands upon which these lessons can be based offer means for district or school-level curriculum designers to incorporate learning progressions throughout grade levels they serve . With the involvement of learning progressions, as illustrated in the AAAS, Project 2061, Atlas of Science Literacy (Volumes 1 and 2), teachers and curriculum planners can more effectively promote continued development of students’ concept formation as they avoid use of redundant topics and lessons from one year to the next .

Color on Wings: Optics of Individual Wing Scales Mohan Srinivasarao*, School of Polymer, Textile and Fiber Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, mohan@ptfe .gatech .edu

The beautiful iridescent colors found on the wings of butterflies have attracted the attention of brilliant minds over the past centuries starting with Newton, who understood that these colors must be due to the

presence of “thin film structures” . Since then, much progress has been made and it is now recognized that many of these brilliant colors are due to various kinds of microstructures present on butterfly wing scale . In other words, the colors are produced by periodic structures of cuticle-air that mimic photonic crystals . These structural colors can include deep blacks, reds, oranges and greens, as well as the more common blues, violets, ultraviolets, and whites . Typically these colors appear metallic due to the saturation or the purity of the colors produced . There have been a number of reports where the “color” of large areas of the butterfly of interest has been studied . Such measurements are subject to a number of inconsistencies due to the fact that the precise a lignment of the scales for different measurements may be difficult and that multiple scale types, with different optical

qualities, are measured together, among other things . In order to avoid such complications, one must perform the necessary optical measurements on single individual wing scales . There have been a few measurements of the optical properties of individual wing scales; however, such studies are quite sparse . Hence we have embarked on a systematic study of the optics of individual wing scales . To characterize the angular dependence of the individual wing scales we used a goniometer with the ability to rotate in all three directions . A single Morpho butterfly scale was mounted at the tip and carefully centered with its long axis parallel or perpendicular to incoming light . The illumination was a white light source and the reflected light was collected via two reflective lenses, equipped with fiber optic leads, which was connected to a spectrophotometer providing the

photo credit Nathan Morehouse

33

reflection/transmission as a function of wavelength . By rotating the scale in this setup we were able to study the reflectance and transmission as a function of angle and compare those results to the measurements in a microspectrometer connected to a microscope . In this talk we will discuss the results of our measurements of individual wing scale reflectance including the polarization dependence .

Iridescence and the Coloration of Butterfly WingsDoekele Stavenga*, Department of Neurobiophysics, University of Groningen, the Netherlands, d .g .stavenga@rug .nl

Iridescence, mediated by multilayer interference, is a widespread phenomenon among insects encountered, for instance, in the cuticle of beetles and damselflies, in the corneal facetlenses of horseflies, in the wing scales of butterflies, and also in the tapetal reflectors of moth and butterfly eyes . In my presentation I will specifically focus on the various coloration principles that butterflies employ: incoherent scattering, multilayer iridescence, and/or photonic crystals . A comparative survey of wing coloration of pierid butterflies, using UV photography and reflectance spectrophotometry, reveals that many pierids display a distinct sexual dichromatism, which can be related to the phylogeny . The optical basis of the wing colors of pierids can be well explained from the structuring and stacking of the scales . While pigment granules cause a diffuse coloration, the directional iridescence of pierid scales is due to multilayered scale ridges . The optics of the scales and wing coloration of lycaenid

butterflies appears to be quite different . The intense, short-wave length iridescence of many blues is caused by multilayers with variable-sized holes in the scale body . It is an interesting question whether the wing coloration of butterflies is related to the spectral characteristics of their visual system .

Dosing Disorder: A Classification of the Visual Effects Developed by Weevils Jean Pol Vigneron, Victoria Welch, and Marie Rassart, University of Namur, Belgium, jean-pol .vigneron@fundp .ac .be

Photonic structures which appear on living organisms are not perfect . However, contrasting the usual engineer’s feeling, these imperfections are not the result of unreliable fabrication processes, but qualities that are maintained throughout evolution at each generation in the species population . These imperfections can then be considered to be part of the optimized diffuse-reflection optical device . The family of weevils known as Curculionidae provides good examples: many of the species in this family are coloured by scales which contain a three-dimensional photonic crystal . However, these photonic structures are usually divided in domains, so that the contents of the scale is better described as a photonic polycrystal than a monocrystal : each grain in the polycrystal is cut from a highly ordered photonic crystal (short-range order), but the orientation of the different grains varies across the scale (long-range disorder) . The size of the domains ranges from the full size of the scale (monocrystal) to the size of the

photonic-crystalperiod in the grain (amorphous structure) . These various levels of disorder can be quantified by the grain size, the coherence length of the structure . The visual effect produced by structures with different coherence lengths include iridescence, metallic colour lacking iridescence, dull colours and whites . Exemples of

weevils which present this wide range of coherence lengths and visual effects will be presented and commented .

Bringing Microwaves to Natural Photonics: The Novel Use of Extra UV-VIS-IR Radiation in the Characterization of an Insect Broadband Reflector Pete Vukusic* School of Physics, University of Exeter, Exeter, United Kingdom, P .Vukusic@exeter .ac .uk

The photonic function of animal ultrastructure is difficult to measure unambiguously . This is invariably due to the often significant variation in alignments of juxtaposed wing-borne or integument-based colour centres . It is also complicated further by the presence of secondary ultrastructural

photo credit: Tony Hisgett

34

or pigmentary components which themselves exhibit elastic or inelastic scattering . Experimental manipulation and characterisation of individual colour centres, such as single lepidopteran scales, is possible in some cases and this improves the

quality of optical data, but it nonetheless has distinct limitations . To this end, we have developed a technique with which it is possible to make much more highly precise experimental measurements of the photonic effect of isolated nanoscale animal ultrastructure . This comprises manufacture of 3D models of animal ultrastructure at appropriately scaled-up dimensions and a measurement of the way in which these reconstructed models interact with microwave frequency radiation . This interaction is analogous to

the optical interaction of original nanoscale animal samples . By using appropriately fabricated models and centimetre wavelength radiation sources therefore, better understanding of the photonic function of animal ultrastructure becomes accessible . The technique has been applied in this instance to the characterisation of a previously unstudied insect broad-band reflector . When used concurrently with conventional analysis techniques, it has provided much clearer evidence about the true nature of the way in which light interacts with the insect’s ultra-structure .

School of Life Sciences Seminar and Plenary: From Morpho to Seurat: Insect Colour Reflections on a Entry to the L’oreal Art And Science of Colour Competition Pete Vukusic*, School of Physics, University of Exeter, United Kingdom, P .Vukusic@exeter .ac .uk

The living world is awash with color costumes that are arranged in innumerable shades, patterns and hues . The vast majority have one fundamental objective in common; namely, they dictate the quality and quantity of light that enters the eye of the beholder . This ability to control light has been central to the evolution of many species, and studies of bright coloration have been critical in elucidating key evolutionary processes for many decades . Through history, art and artists have also relied on the ability to control colour, shade and pattern . The varied representation of objects and scenes in works of art is underpinned by the optical properties and signatures of each

constituent pigmentary or light scattering material that is used . In this sense, a strong connection between visual art and the natural world is unmistakable . Colour, shade and pattern are created and controlled for a specific biological or aesthetic effect . For over a decade, the global cosmetics company L’Oreal have funded a dynamic interaction between science and art by awarding its International Art and Science of Color Prize annually . It is given to artists or scientists in recognition for their work and achievements on the theme of understanding color and its fundamental link between art and science . It was recently awarded to Pete Vukusic, the plenary speaker, for his research into the field of animal colours, specifically the category of colour that is generated when light interacts with microscopic structures on or in animal surfaces . This is referred to as structural colour and has profound importance to many fields of science and to many different technologies . This, the science of structural colour in the living world, and its applicability and relevance to art, is the subject of this lecture .

Iridescence of Rock Dove’s Neck Feather Shinya Yoshioka, Eri Nakamura, and Shuichi Kinoshita, Graduate School of Frontier Biosciences, Osaka University, Japan, syoshi@fbs .osaka-u .ac .jp

Iridescence is observed in various kinds of animals that utilize optical interference phenomenon of microstructures to produce their brilliant colors . In general, the iridescence appears owing to the interference condition that relates

35

the wavelength of the reflected light with the angle of view or incidence . However, the neck feather of rock dove has a very peculiar iridescence: the color change is limited only in two colors, green and purple, and the change occurs very suddenly by only slightly shifting the viewing angle . We have performed microscopic and optical measurements to clarify the origin of this peculiar iridescence . It is found that it is produced by the surprisingly simple physical

mechanism - thin-layer interference . The peculiarity lies in the fact that the higher-order interference condition is satisfied . This causes the sophisticated correspondence in the spectral line shape between the reflectance and the visual color sensitivities of human eye, and results in the two-color nature of the iridescence . The correspondence can be also seen with the absorption maximum of the visual pigments in the rock dove’s vision . In addition, we

have constructed a simple optical system, which can modulate the spectrum of white light to have an arbitrary spectral line shape, in order to further investigate optical and visual effects of thin-layer interference . It is found that the thickness of the thin layer found in the rock dove’s feather is very optimized to cause the two-color nature of the iridescence .

photo credit: Dario Sanches

36

Chrysina Gloriosa May Differentiate Between Circularly, Linearly, and Unpolarized LightParrish Brady±, John Abbott, and Molly Cummings, University of Tex-as at Austin, Austin, Texas, scorpionjeger@hotmail .com

Iridescent cuticles of beetles from the genus Chrysina are one of the few naturally occurring sources of left circularly polarized light . We hypothesize that Chrysina can perceive circularly polarized light differently from unpolarized light, possibly allowing beetles to detect each other while remaining camouflaged from predators . We tested differential flight orientation

of Chrysina gloriosa towards 4 different light stimuli: linearly polarized, unpolarized, and right and left circularly polarized light . We tested 27 individuals, placed in the center of a 20”x20”x13” choice chamber with 1 .5” x 1 .5” slits on each of 3 sides for light presentation . For each trial, the initial flight direction estimate of the beetle was recorded . We alternated filter positions between trials and tested each beetle with two different filter setups . We found significant differences in flight orientation (F = 23 .4, p <0 .0001) between circularly and linearly polarized light, as well as between circularly polarized and unpolarized light (F = 26 .3, p < 0 .0001 .) Beetles

made initial flights significantly more often towards controls (linearly or unpolarized light) than towards either of the two circularly polarized stimuli (mean proportion flights towards control = 0 .58; mean proportion to left circularly polarized = 0 .23; and right = 0 .18), suggesting that circular polarization provides a weaker stimulus than linearly or unpolarized light . Cotrary to our expectations, beetles displayed little preference between right or left circularly polarized light . Controlling for slight variations in differential flux and determining the perceived light intensity of the various polarizations are important next steps in understanding this system .

Optics of Individual Wing Scales of a Blue Morpho: Angle Dependent Polarized ReflectanceMatija Crne±, Saroja Malladi, Vivek Sharma, Jung Ok Park, and Mohan Srinivasrao, Georgia Institute of Technology, Atlanta, Georgia, matija .crne@chemistry .gatech .edu

It is well known, that the color on butterfly scales can be generated in the absence of chromophores . Instead, the spectral characteristics of many butterfly wings are determined by the structure of the scales that comprise the wings . By looking at the butterfly wing of the Morpho butterflies and tilting them, an angular dependence of

PosterABSTRACTS

photo credit: Dick Daniels

37

reflectance is clearly observed . In our work we characterized this phenomenon using a single scale mounted in a microspectrometer . To characterize the angular dependence of the individual wing scales, we used a goniometer with the ability to rotate in all three directions . A single Morpho butterfly scale was mounted at the tip and carefully centered . Perpendicular to this axis were two reflective lenses, equipped with optic fiber leads . One was connected to a light source and the other to a spectrophotometer . By rotating the scale in this setup we were able to study the reflectance and transmission as a function of angle . In addition, we added a polarizer to study the effects of polarization

on the reflectance . The characteristic peak in the reflectance red-shifts in comparison to a 90 degree back-reflectance measurement on a microscope connected to the microspectrophotometer . The polarized spectra show a pronounced difference at longer wavelengths . When the polarizer is oriented perpendicular to the scale axis, the reflectance is much higher than when the polarizer is parallel to the scale axis . In addition to that, the spectra in polarized light had more pronounced peaks . We will discuss the results of these and other measurements in this presentation .

Relationship Between Pale Color and Integument Structure in Chrysina BeetlesKiyoshi Miyamoto1, Motoki Hoshi2, Sachi Miyamoto3, and Akinori Kosaku1, 1Institute of Medical Science, Dokkyo Medical University, Tochigi, Japan; 2College of Agrobiological Resources, University of Tsukuba, Tsukuba, Japan; 3Sano Senior High School, Tochigi, Japan, miyamoto@dokkyomed .ac .jp

The fine structure responsible for surface color in Chrysina beetles, which inhabit tropical rain and cloud forests at altitudes of approximately 1,000 m in the highlands of Costa Rica, were investigated using electron microscopy (JEOL JEM-1011) . The

species examined were gold (silvery yellow) and brown-red colored C. aurigans and the silver (silver-pale blue) C. chrysargyrea . While all of the beetles examined exhibit both metallic and pale colors, we examined only the pale coloration . The epicuticle of the elytra was not homogenous and could be separated into three different layers: (1) superficial layer without any particular structure measuring several-hundred nm in thickness, (2) multilayer: several-dozen very thin (50-100 nm) layers exhibiting low electron density, and (3) multilayer: several thick (100-300 nm) layers exhibiting higher electron density . The pitch of multilayer (2) was observed to vary with distance from the surface . For the convenience of analysis, multilayer (2) could hypothetically be divided into upper, middle, and lower parts . Each part of multilayer (2) was thought to affect the color of the beetle due to light interference, procuring colors that ranged from the visible to ultraviolet wavelengths . Conversely, the colors that arose due to interference by the layers of multilayer (3) ranged from red and to ultrared . The colors produced by the upper, middle, lower parts of multilayers (2) and (3) agree well with those observed in living beetles .

photo credit: Amada44

38

Effects of Rearing Condition and Age on Iridescent Coloration in Battus Philenor Alexandra C. Nahm± and Ronald L . Rutowski, Arizona State University, acnahm@asu .edu

Conventional wisdom holds that in butterflies the dorsal wing surface coloration may be used in intersexual communication while the ventral wing coloration is a warning signal intended for predators, especially in distasteful species . The Pipevine Swallowtail butterfly, Battus philenor, bears iridescent patches on the ventral and dorsal hindwing surfaces . The ventral iridescence is part of their aposematic coloration while the dorsal iridescence is believed to serve as an aid for selection of a mate . This permits an assessment of if and how function might shape the properties of iridescent color signals . We collected spectra from both dorsal and ventral wing surfaces of lab- reared and field-caught individuals . Brightness, intensity, hue and chroma were extracted from the spectra to describe and compare the coloration of the two sexes and the two the wing surfaces . The ventral hindwing iridescence differs little among the sexes as might be expected of an aposematic signal . The dorsal hindwing iridescence is restricted to males, again suggesting it is a sexual signal, and is much less much bright than that of the ventral hindwing iridescence of both sexes, perhaps due to differences in the ecological circumstances in which the signals are displayed . Lastly, age affects the iridescence on the ventral hindwing surface more than that of the dorsal hindwing surface .

Adaptive Variation of Iridescent Plumage Coloration in Magpies (Pica Pica) Hyun-Young Nam±1, Chang-Yong Choi1, Jihoon Lee1, Sang-Im Lee1, Jae Chun Choe2, 1Seoul National University, South Korea, 2Ewha Womans University, South Korea, stern0223@lycos .co .kr

Black-billed magpies (Pica pica) have weak bluish/greenish iridescence on their black plumage of wing and tail . Recent studies have showed that coloration by feather microstructure indicates good quality in sexual selection though some species of them were previously known as sexually monochromatic birds, and elongated tail feathers of magpies are related with body condition . Therefore we compared their quality indices with coloration by age/sex/breeding status . We investigated variation of iridescence color in feather whether 1) it indicates sex and/or age status and 2) it can be a conditiondependent character in the chosen sex of breeding individuals and 3) it fluctuates under variable climate conditions . Both bluish wing coloration ranged UV-blue and greenish tail coloration ranged out of UV region were related with both age-sex status, however, in contrast to our prediction that UV-directional coloration will act as an sexually selected characteristic, greenish tail coloration only had relationship with body condition and reproductive success of breeding males . Tail coloration also had relationship with climate fluctuations . In the area where climate is more fluctuated, variation of tail color tend to higher than wing color or other physical characters which do not indicate body condition . We

39

concluded from these results that tail coloration of male magpies may act as a quality indicator in context of sexual selection .

Spec(Tac)Ular Beacon Signaling of Iridescent Butterflies Primoz Pirih±1, Mojca Stojan-Dolar2, Bodo Wilts1,3 and Doekele G . Stavenga1, 1University of Groningen, Groningen, the Netherlands; 2 German Primate Center, Göttingen, Germany; 3University of Goettingen, Goettingen, Germany, p .pirih@rug .nl

Insects (e .g . beetles, damselflies, and most notably butterflies) build multilayer structures in order to produce iridescent colouration, reflecting in the UV-A to green spectral range (320 . .550 nm), but use pigments to produce long-wavelength colouration . While pigmentary colouration is usually diffuse-reflecting, iridescence represents more or less specular reflections . The most advertised showcase of blue iridescence is presented by the neotropical Morpho butterflies, whose lighthouse-like blue flashing may be appreciated both in relatively open spaces and in dense tropical forests . Here, we explore the hypothesis that specularity may be used as means of directing -and thus enhancing the visibility of the colour signal . We report on our field work in Peruvian Amazonia, where we observed behaviour of morphos and related their activity to environmental parameters (e .g . terrain openness, illumination conditions) . We describe basic activity patterns which indicate the employed strategy of signalling and develop a simple model for the distribution of the reflected signal into the environment . We discuss the general properties

40photo credit: Brian Gratwicke

41

of the beacon signalling strategy in species from different groups of butterflies (Morphinae, Lycaenidae, Pieridae) and the link between the beacon signalling and butterfly vision .

Evolution and Reuse of Iridescent Structures in ButterfliesShelley Wickham, Leon Poladian, Maryanne C .J . Large, and Lars S Jermiin, University of Sydney, Australia, leonp@maths .usyd .edu .au

The diversity of 2D optical microstructures found in butterfly wing scales exhibit modifications to the basic multi-layer structure with observable changes to the iridescence . Here, we optically characterise examples of three variations of multi-layer structure, as found in 10 species . The modifications involve, respectively, the elaboration of ridge-lamellae and microribs . A third modification uses tilted ridges . It appears that some modifications enhance iridescence (possibly for signaling) while others suppress the iridescence (possibly for camouflage). In addition, we consider the phylogeny of the butterflies, and are thus able to relate the optical properties of the structures to their evolutionary development from a common primitive version . Of particular interest has been the issue of why structures recur in the evolutionary tree . It is possible that the evolutionary ‘cost’ involved in losing a complex structure or modification is much less than in gaining it in the first place . This possibility can be assessed by using a ‘Dollo’ parsimony analysis . Both simple and Dollo parsimony analyses were used,

42

allowing the mechanism of adaptation to be addressed . Simple parsimony suggests convergent evolution of one structure, while Dollo parsimony implies that ‘latent’ structures can be reused .

Hardness and Elastic Properties of Iridescent ScalesJacqueline Hayes, Maryanne C .J . Large, Leon Poladian, and Mike Swain, University of Sydney, Australia, leonp@maths .usyd .edu .au

It is easy to assume that iridescent structure might have evolved under selective pressures associated with their spectral appearance . However, this neglects the possibility that the structures may have other roles, or perhaps that they have been “seconded” to serve an optical function . Here, we study

the elastic modulus and hardness of butterfly scales for the first time through nanoindentation and correlate mechanical properties to the type of iridescent structure . Butterfly scales are complex structures made from dry insect cuticle . Because the scales were highly compliant the residual depth of penetration of the indenter tip was accurately measured using three-dimensional visualization of the impression . The mechanical properties are largely dependent on the microstructure of the scale . Scales with a multilayer stack in the ridges of the scale had the highest elastic modulus and hardness . Scales with an ordered three-dimensional crystal structure had a lower elastic modulus and hardness . Moreover, there were scales that did not respond normally to indentation . Scales with an

three-dimensional, photonic crystal in the body of the scale fractured when indented, and scales with a multilayer stack in the body of the scale bent when indented . In addition, different parts of the scale respond in different ways to indentation, suggesting specific functions for each part .

Structural Colour and Thermoregulation in ButterfliesStephen G . Bosi, Jacqueline Hayes, Maryanne C .J . Large and Leon Poladian, University of Sydney, Australia, leonp@maths .usyd .edu .au

It has been hypothesized several times in the literature that the colour (including the presence or absence of structural colour) of butterfly wings imbues them with photothermal properties that assist in thermoregulation . It has also been suggested that loss of iridescent/structural colour increases solar absorptance and so may represent a selective advantage in cold, harsh climates . This paper refutes both aspects of this hypothesis . 64 species of butterfly in the families Geometridae, Lycaenidae, Nymphalidae, Papilionidae, Pieridae, Sphingidae, Uraniidae and Zygaenidae were obtained . The specimens were divided into two groups; 36 iridescent and 28 noniridescent specimens . The solar absorptance of their wings was measured spectrophotometrically from 250 nm to 2600 nm . For each specimen, the long term 24 hr mean temperature for the month and location of capture was obtained . Contrary to the hypothesis, a plot of solar absorptance versus habitat temperature did not show a trend of decreasing absorptance

photo credit: Charlesjsharp

43

with increasing temperature . Moreover, it was found that the iridescent butterflies exhibited on average, significantly higher solar absorptance (0 .68) than noniridescent butterflies (0.43).

Photo-Real Rendering of Iridescence from Thin Films in Feathers on Birds Mark J. Prusten, Silicon Arts, Tucson, Arizona, photondyn@silicon-art .com

The most highly developed examples of iridescence found in terrestrial animals is birds and insects . The two groups frequently interact; birds are among the principal predators of insects . In this paper, the mechanics of iridescence are described for the structures of feathers in birds and models are made for the development of High Dynamic Range Images, HDRI, photo-real shaders . The simulation of iridescent qualities of the hair and feathers of birds is developed . The modeling and rendering of the feather structures incorporate thin film multilayer optical stacks . Whether a color is iridescent depends on the part of the feather that generates it: barbs produce

non-iridescent colors, barbules iridescent ones . In some animals, iridescence is a result of fine incised lines on a surface but in birds (and many insects), they result from the same multi-layer refraction that gives rise to blue and green . The influence of sub-surface scattering, global illumination, final gathering and spectral rendering and the influence of pockets of air inside the feathers that scatter all wavelengths of light will be examined . The brightness of the white for example depends on the number and distribution of those pockets . The simulation of the polarized light and the interaction of the insects with classic lighting setup will be reviewed were the illumination varies greatly in spectrum and intensity .

Quantifying Iridescent Coloration: A New Apparatus and Comparison of TechniquesMelissa Meadows Rader, Nathan Morehouse, Ronald Rutowski, Jonathan Douglas, and Kevin McGraw, Arizona State University, Melissa .Meadows@asu .edu

Most animal colors are easily quantifiable by a variety of well- established techniques . However, iridescent colors, with their shifts in hue and brightness caused by minute changes in viewing geometry, present a challenge . In order to measure color in a repeatable, biologically-relevant way, we developed a new apparatus that allows for continuous variation of viewing geometry . We also examined the efficacy of several commonly-used color measurement methods, and arrived on a method for measuring iridescent hummingbird

feather coloration with high repeatability (hue: 0 .92, brightness: 0 .65, red chroma: 0 .95) and that is biologically meaningful, taking into account the potential for signal optimization and feather color variation between feathers within an individual .The apparatus will be present for demonstration during the poster session .

Quantitative Analysis of Passive Color Changes in Dynastes Hercules (Coleoptera)Marie Rassart and Jean Pol Vigneron, University of Namur, Belgium, marie .rassart@fundp .ac .be

The large South-American beetle Dynastes hercules lichyi undergoes passive colour transformations, changing from khaki-green to deep black when the ambient humidity is increased . Such a darkening probably improves the insects’ camouflage at night, when most of the light is lost and humidity is getting high . This communication essentially reports on a study of the physical aspects of this colour change, and on its possible implications for material sciences . We first recorded the optical reflection factor of the cuticle of these Dynastes under various stabilized hygrometric conditions, providing a photometric description of the progressive coloration loss near 80% humidity . In parallel, scanning electron microscope nano-morphology investigations of the cuticle allowed to determine the structure of the hygro-adjustable coloring layers . The dry structure is essentially a wide-period Bragg multilayer which alternates chitin sheets and void layers . A two- dimensional, disordered, array of

photo credit: Surya Prakash

44

rods normal to the cuticle surface maintains the rigidity of the structure . The khaki-green coloration is explained by the second-order multilayer photonic gap which opens near 500 nm and the black appearance is shown to result from water infiltration through cracks in a thick protecting transparent wax layer covering the photonic structure . The color change is explained by the attenuation of the refractive index contrast, which permits the incident light to reach the deeper absorbing melanin substrate . This mechanism was confirmed by 3D transfermatrices simulations . It is suggested that these natural structures, in which the optical properties are controlled by moving fluids, can be synthesized with already known mesoporous materials . The resulting hygrochromic surfaces could have a variety of uses in sensing or displaying applications .

Effects of Diet on Male Coloration in a Jumping Spider (Habronattus Pyrrithrix)Lisa A. Taylor1, Kevin J . McGraw1, and David Clark2, 1Arizona State University, 2Alma College, Alma, Michigan, Lisa .A .Taylor@asu .edu

In many animals, conspicuous male coloration is thought to function as an honest indicator of mate quality . In Habronattus pyrrithrix, females are dull and inconspicuous, while males have a brilliant red face, green leg tufts, and white pedipalps that they display to females during courtship . Our previous work suggests that the red coloration of males is condition-dependent in a wild population, and thus has the potential to function as a quality indicator . When color is condition-dependent, it may be an honest signal of the nutritional condition and foraging ability of its bearer . If so, we expect that enhancing the quality of a male’s diet would enhance his coloration . In Experiment 1, to

understand how juvenile diet affects development of adult male coloration, we reared juvenile spiders on either high or low quality diets, and measured their coloration at maturity . In Experiment 2, to understand how adult diet affects the maintenance of coloration, wild caught adults were fed either high

or low quality diets, and their coloration was me sured after 45 days . In Experiment 1, male’s faces tended to be redder in the high quality diet group than the low quality group suggesting that condition-dependence of red coloration may be mediated by juvenile diet . In Experiment 2, diet had no effect on red coloration suggesting that adult diet is unlikely to be important in maintaining this coloration . Green leg tuft and white pedipalp coloration were unaffected by diet in either experiment, suggesting that these colors may be less likely to signal aspects of nutrition .

Effects of Food Stress on Iridescent Signaling in Battus Philenor Kimberly Vann±, Alexandra Nahm, and Ronald Rutowski, Arizona State University, knvann@asu .edu

Male pipevine swallowtail butterflies, Battus philenor, have iridescent patches on the dorsal and ventral hindwings, while females have iridescent patches only on the ventral surface . The ventral patches have apparent function as warning signals, and the dorsal patches as a signal of quality for mate choice . The condition dependence of these signals will give insight into their function . The condition dependence of the iridescent signals is expected to be greater for the dorsal surface than the ventral surface, because of the differences in the assumed functions . Two treatment groups of larvae were removed from host plant (Aristolochia watsonii) during the third and fourth day of the final larval instar, and a third treatment group was allowed to feed through pupation . Adults resulting from these larvae were measured, weighed, and the colors analyzed

photo credit: Kati Fleming

45

through spectrophotometry . Food deprivation leads to smaller adult body size as measured by forewing length and body mass .

Multi-Physics Description of the Day-Flying Moth Cocytia D’urvilleiJean Pol Vigneron and Marie Rassart, University of Namur, Belgium, jean-pol .vigneron@fundp .ac .be

In chapter 30 of his book on the exploration of the Malay Archipelago (1869), Alfred Russel Wallace underlined the outstanding appearance of a local day-flying moth, Cocytia d’Urvillei . Exploration at the submicron scale showed that this moth has developed several photonic and hydrophobic structures: (1) the clear wings show a dense array of cylindrical protrusions which is possibly an optimized trade-off between an antireflection coating and a water-repellent structure, (2) the black areas on the wing veins and magins are covered by absorbing scales, where the ridges and cross ribs are minimized, for the probable purpose of optimizing access to a granular broadband absorber on the scale’s ground membrane; (3) the dorsal side of the abdomen is spectacularly iridescent, selecting yellow to cyan reflections . Scanningelectron microscope examination of the long scales which produce this iridescence revealed a structure very similar to that found on the wings of the Morpho butterflies . This observation on organisms that appear to be so distant (geographically and phylogenetically) suggests that this type of photonic construct is very generic and highly constrained by bio-fabrication steps .

Multi-Scale Optical Response of Structured Surfaces in Living OrganismsJean Pol Vigneron and Marie Rassart, University of Namur, Belgium, jean-pol .vigneron@fundp .ac .be

Natural photonic structures are complex objects : their geometry reveals several length scales, with different orders of magnitude . In principle, a complete vector-wave description of the optical response of structure should be applied, but in many situations, the scattering surface is too large and too complex to warrant any feasible approach . In a butterfly wing such as that of the Brazilian butterfly Cyanophrys remus, for instance, a single ventral scale contains a photonic polycrystal, made of highly structured grains with a distribution showing long-range orientation disorder . The scales themselves are implanted at various angles

and orientations on the wing membrane, and the wing membrane shape keeps some memory of its folding at the time of the exit from pupa . The visual effects determined at all these length scales are important to biology and should be consiered, even if approaching this from ab initio Maxwell’s equations is unfeasible . We propose an hybrid approach for calculating the reflectance spectra from such complex surfaces, which combine Monte-Carlo ray tracing for long-paths propagation and fully vectorial multiple scattering of electromagnetic wave for local color filtering . The procedure has been applied to explain the light scattering properties of several insect’s coloring structures exhibiting short-range order and long-range disorder, and the simple case of an hemispheric multilayer,as found on the cuticle of the brightly colored African shield-backed bug beetle Calidea panaethiopica.

46

AbstractSUBJECT INDEX

photo credit: Charlesjsharp

47

Birds: Pages 18, 19, 22, 23, 24, 26, 28, 30, 34, 38, 41

Butterflies and moths: Pages 19, 20, 22, 24, 25, 27, 32, 33, 36, 38, 39, 40, 42

Color Measurement, color change, and color usefulness: 19, 20, 22, 24, 27, 28, 29, 34, 36, 38, 39, 40, 41, 42, 43

Education and Application: Pages 21, 26, 27, 29, 31,

Environment and conditions / Evolution: Pages 18, 19, 20, 22, 23, 24, 25, 26, 28, 30, 34, 36, 38, 39, 41, 42,

Insects / spiders: Pages 25, 26, 29, 30, 33, 36, 37, 42

Mechanisms and Measurement / scale and feather structure: Pages 18, 19, 20, 22, 23, 24, 25, 27, 29, 30, 32, 33, 34, 36, 37, 39, 40, 41, 43