I LLINIUNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN

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Natural History SirveyLibrary

SUMMER EPHEMEROPTERA, PLECOPTERA, AND TRICHOPTERA (EPT)SPECIES RICHNESS AND HILSENHOFF BIOTIC INDEX AT EIGHT STREAM

SEGMENTS IN THE LOWER ILLINOIS RIVER BASIN

Dr. R. Edward DeWalt and Dr. Donald W. WebbCenter for Biodiversity

Illinois Natural History Survey607 East Peabody DriveChampaign, IL 61820

TECHNICAL REPORT 1998 (9)ILLINOIS NATURAL HISTORY SURVEY

CENTER FOR BIODIVERSITY11 May 1998

PREPARED FOR

United States Geological SurveyNational Water Quality Program

Urbana, IL 61801

ABSTRACT

Adult Ephemeroptera, Plecoptera, and Trichoptera (EPT) species were collected from eight

lower Illinois River basin streams sites during June, July, and August 1997. A total of 17,889

specimens were collected, comprising 67 species in 17 families. Caddisflies, or Trichoptera, were

dominant both in the number of species (40 species) and in abundance (88.3% of all individuals).

Mayflies (Ephemeroptera) contributed far less to species richness and abundance, while most

streams were nearly devoid of stoneflies (Plecoptera). Log 0oEPT species richness differed

significantly across stream sites (ANOVA, F=12.61, p=0.0001), and peak in July (ANOVA,

F=67.69, p=0.0001). Hilsenhoff Biotic Index (HBI) was not significantly different across stream

sites (Fig. 5, ANOVA, F=0.89, p=0.53). However, mean monthly HBI scores were highly

significantly different (ANOVA, F=4.99, p=0.008), with July being closest in score to the HBI

calculated over all species collected for the summer. All basin sites rated as at least "fair", based on

Hilsenhoff's scale. Virtually no difference in mean total HBI values existed between large and

small streams (4.86 and 4.71, respectively). Several weaknesses exist in using a taxonomic

richness metric or a biotic index alone. We suggest that both be used in concert to assess stream

health. Where ever possible, multiple light traps samples over a season should be used to

encompassed more variation in the metrics. If only one can be taken, early in July seems to be the

time frame to produce results closest to season-long investigations.

INTRODUCTION

Monitoring stream ecosystems using aquatic macroinvertebrates has been an effective tool

for documenting changes in community health (Plafkin et al. 1989). Some macroinvertebrate

indices of stream health have been identified as most useful and efficacious. These include the

EPT index (sum of Ephemeroptera + Plecoptera + Trichoptera species richnesses, Lenat and

Penrose 1996), total macroinvertebrate taxa richness (Plafkin, et al. 1989), and several numerical

biotic indices (Hilsenhoff Biotic Index, or HBI of Hilsenhoff 1987, and the North Carolina Biotic

Index, or NCBI of Lenat 1993). Wallace et al. (1996) recently endorsed the EPT index as

possibly the most efficient of the macroinvertebrate indices. Similarly, Barbour et al. (1992)

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compared a large number of macroinvertebrate indices and found that simple species counts,

especially those of sensitive taxa, were most effective at determining impairment of streams.

Aquatic stages of EPT taxa are most often used for stream monitoring. However, this

leads to underestimates of the EPT assemblage in a stream segment since immature stages are often

identified only to the generic level. Most identification keys to the species level focus on the adult

stage.

Illinois is fortunate to have published, statewide monographs on their EPT fauna. Frison

(1935) published a classic treatment of the stoneflies (Plecoptera) of Illinois. Shortly thereafter,

Ross (1944) presented his "Caddisflies (Trichoptera) of Illinois." The mayflies (Ephemeroptera)

of the Illinois was published by Burks (1953). The information gathered by Illinois Natural

History Survey (INHS) researchers on these EPT taxa is unsurpassed in any region of the country.

Despite this vast knowledge, the number of EPT taxa cannot be reliably estimated for any particular

stream reach in Illinois since these studies were for the purposes of gathering specimens for

taxonomic treatment of the orders not for ecological purposes.

The Illinois River basin drains much of what was the wet-prairie region of central Illinois.

Lack of detailed benthic studies in the central and western part of the state precludes knowledge of

"typical" EPT composition there. However, Ross (1944), Burks (1953), and Frison (1935)

generalize about the fauna of large and small rivers in Illinois.

The USGS- National Water Quality Assessment (NAWQA) program has targeted the

Illinois River system for study. The long-term goals of this program are to describe the status and

trends in the quality of a large, representative part of the Nation's surface- and ground-water

resources, and to provide a sound, scientific understanding of the primary factors affecting the

quality of these resources. Several sampling stations in the lower Illinois basin have been

established, benthic macroinvertebrate samples collected and are now being processed. Results of

these studies are expected to require much time to compile. Collection of the adult EPT species at

these sites would provide a rapid view of local river health and provide a species list to guide

identifications of the immature stages found in benthic samples.

Our objectives were to use summer-emerging EPT species to characterize the biotic

integrity of eight NAWQA sites in the lower Illinois River basin. Use of a second measure of

biotic integrity, the HBI, allows for direct comparison of the performance of both indices.

Questions asked were 1) How do the EPT and HBI indices vary throughout the summer months?

2) Do EPT and HBI vary significantly with the number of individuals sampled? 3) Are there

differences in EPT and HBI between sites?, and 4) Do EPT and HBI say the same things about the

streams in which they are used. These collections will also aid in the identification of immature

insects taken in benthic samples. A search of Frison (1935), Ross (1944), Burks (1953) and

databases at the INHS will also provide a historical assemblage for sites in the Illinois River basin.

METHODOLOGY

Eight existing NAWQA sites were chosen in the lower Illinois River basin to survey for

EPT species (Fig. 1, Table 1). These sites correspond with local benthic macroinvertebrate

sampling efforts. Adult EPT were trapped from areas adjacent to the stream using a BioquipTM

AC/DC 12 volt ultraviolet collecting light during June, July, and August of 1997. This apparatus

was suspended 1 m above the ground so as to reflect off a vertically hung white sheet. Two 20 cm

X 30 cm white plastic trays placed below the sheet trapped insects in a pool of 80% EtOH. The

light trap ran for 1 hr beginning at sunset. Air temperature was monitored at most sites at the

beginning and end of the 1 hr period.

Caddisflies struck the sheet several times and fell to the trays below. However, mayflies

and stoneflies required some additional care to obtain high quality specimens. Mayfly sub-adults

(subimagoes) were collected directly off the sheet and placed into styrofoam cups, where they were

held until they had transformed to the imago, a terminal stage of development. They were then

preserved in 80% EtOH. Several species of male stoneflies require eversion of internal genitalia

before they can be successfully identified. Males of Perlesta sp. and Isoperla sp. were picked from

the sheet and their lower abdomens squeezed gently until their genitalia extruded. The entire insect

was then immersed in 80% EtOH, maintaining extrusion of the genitalia, until the insect no longer

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struggled. These males were stored in separate vials. The trays of insects were then poured into a

11 container for transport back to the laboratory.

Adults were subsampled, where appropriate, and sorted into vials. Specimens were

identified to species in most cases. Females could not be identified to species in some cases. All

data was entered into an ExcelT database and analyzed using the Statistical Analysis System (SAS

1985). The dataset was sorted by location and month, the percentages for each taxon calculated,

and the total numbers of EPT taxa counted. The HBI is a Midwest index of stream organic

pollution (Hilsenhoff 1987). Tolerance values have been assigned to many taxa that range from 0

to 10, with higher numbers indicating a greater tolerance for organic pollution. Tolerance values

were only available at the genus level for some species, e.g. caddisfly genera Cheumatopsyche

and Hydroptila. Tolerance values were absent for some species entirely, necessitating removal of

those species from the HBI calculations. All taxa encountered and their assigned tolerance values,

are provided Table 2. The influence of month and site upon EPT and HBI values was investigated

using the General Linear Models (GLM) approach of Analysis of Variance (ANOVA, SAS 1985).

Logio transformations of data eliminated the discrete nature of the EPT count. A Duncan's Multiple

Range Test (SAS 1985) was used to determine relationships between sites and months for EPT

and HBI parameters. The ANOVA was an exploratory analysis and its conclusions should be

accepted with care. Small sample size (degrees of freedom = 32, 8 sites and four "month" levels

including total, June, July, and August EPT and HBI) may pose a problem with interpretation.

We used the Spearman Rank Correlation (SAS 1985) to investigate the relationships

untransformed HBI values to that of the EPT and its components.

Most specimens were accessioned into the INHS collections as vouchers for the study. All

specimen-level data from voucher specimens (species, location, numbers, etc.) have been added to

searchable Ephemeroptera, Plecoptera, and Trichoptera databases maintained by the INHS.

RESULTS

Dates of collection, times, temperatures, and total counts corrected for subsample rates are

presented in Table 3. Ultraviolet black light traps yielded 17,889 subsampled EPT adults and 67

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species over the summer, 1997 sampling period (Table 4). Trichoptera contributed 61.2% (41

species) of this total, while mayflies provided another 34.3% (25 species). Stoneflies were a

relatively minor component of the EPT fauna, contributing only 4.5% (3) of the total.

Abundance: Abundances, standardized for subsampling effort and to a 1 hr collection period

were extremely variable across sites sampled (Table 3). Mean values of log 0o adjusted abundance

were not significantly different across sites (ANOVA, F=1.23, p=0.35). It is probable that a low

degrees of freedom obscured abundance relationships. However, larger rivers (Sangamon River at

Oakford, Mackinaw River, Illinois River at Starved Rock) accounted for three of the top four mean

abundances. Smaller streams either supported lower densities or provided less visible area around

the ultraviolet light trap. Significant log 0l abundance differences were found across months

(ANOVA, F=6.10, p=0.01). A Duncan's MRT produced the following relationships :

Duncan Grouping Mean N MonthA 3.40 8 July

AB 3.03 8 AugustB 2.57 8 June

June and July were the only months with different abundances. July and August mean air

temperatures, taken during sample visits, were 14-15% warmer than during June. This would

reduce the numbers of insects flying in June. Additionally, most of Illinois had experienced a

cooler-than-normal spring which delayed the development of adults until July.

Dominant taxa: Three of four large stream sites (Illinois River sites, Sangamon R. at Oakford,

Mackinaw River near Green Valley) were dominated by species of net-spinning caddisflies in the

family Hydropsychidae (Fig. 2). Chief among these was Potamyiaflava (Hagen) whose percent

contribution over the entire summer ranged from 16 to nearly 55%. Ross (1942) characterizes this

species as a large river inhabitant, often of great abundance. We have personally witnessed this

tawny species emerging in large numbers from the shores of the Mississippi and other large rivers

in the state. Hydropsyche bidens Ross was common at three of the four sites. Ross (1944) found

no definite association with stream size for this species. Cheumatopsyche sp. was an abundant

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taxon at all stream sites. Most of the individuals were females whose identity was impossible to

ascertain. Males were identified as Cheumatopsyche lasia Ross, C. campyla Ross, and C. pettiti

(Banks). Ross (1944) found that C. lasia and C. pettiti most often occurred in small streams, but

could be found in large rivers as well. Cheumatopsyche campyla has a preference for large rivers.

Small-to-medium streams demonstrated much less overlap in dominant taxa than did large

streams (Fig. 3). Cheumatopsyche sp. was found at three of the four sites. Again, most were

unidentifiable females. Sometimes all three species found in large rivers were also present in the

smaller ones. However, C. pettiti was often the most common of the three. Nectopsyche sp. were

commonly taken in these streams. Females were unidentifiable to species and were most often the

bulk of the individuals. When males were present, N. candida Ross and N. diarina Ross were

the abundant species. Ceraclea sp. were dominant at three of four sites, and were almost

exclusively composed of C. tarsipunctata and C. transversa. Both species have been collected

throughout the state in a wide variety of stream sizes (Ross 1944; Moulton and Stewart 1996).

Species Richness: Log 0oEPT species richness (Fig. 4) differed significantly across stream sites

(ANOVA, F=12.61, p=0.0001). A Duncan's MRT (a=0.05) found the following relationships:

Logl0Duncan Grouping Mean EPT N Site

A 2.39 4 IndianA 2.36 4 Mackinaw

AB 2.31 4 Sangamon-MonticelloAB 2.31 4 PantherBC 2.25 4 La MoineBC 2.24 4 Illinois-Starved RockCD 2.16 4 Illinois-FlorenceD 2.10_ 4 Sangamon-Oakford

Generally, small and medium-sized streams had the highest EPT values. Indian Creek displayed

the highest overall richness at 38 species, while the medium-sized La Moine River tallied only 21

total EPT (Fig. 4). The Mackinaw River was the most diverse large river. It produced 41.9%

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more EPT than the Sangamon River at Oakford, which had the lowest EPT richness of the large

rivers (Fig. 4).

LogD0 of EPT species richness was also different across months (ANOVA, F=67.69,

p=0.0001). A Duncan's MRT demonstrated three distinct groupings (a=0.05) with the following

relationships:

Duncan Grouping Log 0o N MonthMean EPT

A 2.45 8 TotalB 2.30 8 JulyB 2.24 8 AugustC 2.07 8 June

The month "Total" represents a count of all species for a particular site. It is not surprising then

that this EPT tally forms a distinct grouping. July and August values were not significantly

different, but June EPT totals were significantly different from both months. Most EPT species

were cued to emerge in July this particular year--the cool spring delaying transformation of larval

stages to adults until that time.

Hilsenhoff's Biotic Index: There were no significant differences in mean HBI scores across

stream sites (Fig. 5, ANOVA, F=0.89, p=0.53). However, mean monthly HBI scores were

highly significantly different (ANOVA, F=4.99, p=0.008). A Duncan's MRT produced the

following relationships among monthly means:

Duncan Grouping Mean N MonthA 5.33 8 August

AB 4.78 8 TotalB 4.53 8 JulyB 4.23 8 June

This is a complex relationship, but the most obvious outcome is that June had a significantly lower

(greater health/quality) HBI score than did August. All other relationships cannot be clarified at

this time; however, it appeared that HBI scores increased as the summer waned. Late season

dominance by such species as P. flava and the several Cheumatopsyche species produced higher

values in August. Species with lower tolerance values dominated in June. Total HBI values are

the most appropriate ones on which to base decisions, since they represent the average tolerance of

the whole community. Given a similar thermal regime, July might be the best month to estimate

tolerance of the entire community if only one monthly sample could be collected. Hilsenhoff

(1987) presented the following ranges and quality designations.

HBI Ranges Quality Rating0.00-3.50 Excellent3.51-4.50 Very Good4.51-5.50 Good5.51-6.50 Fair6.51-7.50 Fairly Poor7.51-8.50 Poor8.51-10.00 Very Poor

Total HBI values are the most appropriate measures of biotic integrity since they encompass the

entire summer fauna. These are provided along with tentative ratings from Hilsenhoff (1987).----------------------------- - ----------- --Qua----Total HBI Quality

Site Score RatingMedium-to-Large Rivers

Mackinaw 4.87 GoodIllinois -Starved Rock 4.63 Good

Illinois-Florence 5.52 FairSangamon-Oakford 4.40 Very Good

Small-to-Medium RiversSangamon-Monticello 4.93 Good

La Moine-Colmar 4.07 Very GoodIndian 5.14 Good

Panther 4.69 Good

All sites were rated as at least "fair", having scored 5.50 or below. Virtually no difference in mean

total HBI values existed between large and small streams (4.86 and 4.71, respectively). The

Sangamon River at Oakford and the La Moine River at Colmar were rated at "very good" by the

HBI. This is disturbing since these sites demonstrated low EPT taxa richness.

Relationships of HBI, EPT and its Components: A Spearman Rank Correlation (n=32)

found very low correlations of HBI and EPT values:

Variables HBI EPT EPHEM PLEC TRICH ADJABUNDHBI 1Fm PT 1

EPHEM 0.33PLEC -0.39TRICH 0.26ADJABUND 0.10

1-0.154 1

0.45 0.06 10.39 0.37 0.24 1

Additionally, no components of the EPT index were found to have a predictable (inverse)

relationship with the HBI. This was possibly due to the heavy weighting of abundant species in

the calculation of the HBI and the fact that a large percentage of EPT taxa were represented by

relatively few individuals. Trichoptera and Ephemeroptera richnesses were highly correlated with

the EPT index. Plecoptera were not abundant in most streams and usually were represented by

only one or two species. This accounted for its low correlation to the EPT index. The variable

"adjabund" is abundance adjusted for subsampling effort. It showed a positive, but small

relationship to any of the HBI and EPT indices, demonstrating that the number of individuals had

only a minor effect on these indices of stream health.

Notes on Species Encountered: Only 6 of the 31 baetid mayflies known from Illinois (Burks 1953,

McCafferty website: www.entm.purdue.edu/entomology/mayfly/mayfly.html) were collected or

historically known from the sample locations. Species records in Burks (1953) and in about 4000

database records of Ephemeroptera at the INHS showed that only Callibaetisfluctuans (Walsh) had

been previously reported from the area. We recorded five species at four of eight sites in medium-

to-small rivers and streams (Table 4). Three of the six caenid mayflies known to occur in Illinois

were taken from these silty prairie streams. Some species, such as Caenis hilaris (Say) and C.

latipennis Banks were dominant inhabitants across all stream sizes. The Sangamon River at

Monticello produced huge numbers of C. latipennis during August. Heptageniid mayflies

accounted for 10 species (26 known from Illinois, Burks 1953, Bednarik and McCafferty 1979),

the most common of which being Stenacron interpunctatum (Say). This species occurred in both

large and small streams and is tolerant of siltation and low dissolved oxygen (Hilsenhoff 1987,

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Lenat 1993). Isonychia rufa McDunnough, one of five Isonychia to occur in Illinois and an

inhabitant of the swifter portions of streams, was documented at several sites across all stream

sizes. Only the males of this species can be identified. Female specimens identified to Isonychia

were probably this species. Burks (1953) and Kondratieff and Voshell (1984) characterize the

genus Isonychia as a common inhabitant of prairie streams in the Mississippi River drainage.

Species richness of stoneflies was very low for the study area. Seven summer-emerging

(perlids and perlodids) species are historically known from the drainage (Table 4), but only

Perlesta decipiens (Walsh) and Isoperla bilineata (Say) widely occur in the region during summer.

Snellen and Stewart (1979) reported a lengthy egg diapause in P. decipiens (as P. placida

(Hagen). Hynes (1961) postulated that this type of diapause may permit drought resistance and

avoidance of competition for food and space. It may also allow for avoidance of high summer

water temperatures and the concomitant low dissolved oxygen concentrations. No such study had

been conducted for L bilineata. It is disturbing that no specimens of Acroneuria, Agnetina, or

Neoperla were collected. Species in these genera may have experienced drastic declines in Illinois

during the last several decades.

Three families contributed the largest number of caddisfly species during the study. These

were the hydropsychids, hydroptilids, and the leptocerids. Twelve species of hydropsychids were

collected or have been known to occur at or near the sites sampled. Ceratopsyche bronta (Ross)

was a dominant species at the two smallest streams, Indian and Panther Creeks. Ross (1944) and

Schefter and Wiggins (1986) report this species frequents cool, headwater streams and is tolerant

of moderate organic enrichment. Although Ross (1944) discusses some preferences of

Cheumatopsyche species for large or small streams, our data suggests that the three species

encountered have wide ranges of stream size preference. Cheumatopsyche lasia Ross has been

noted to be abundant in heavily silted streams throughout the central prairie of North America

(Ross 1944, Moulton and Stewart 1996). Hydropsyche betteni Ross occurred only in small-to-

medium-sized streams, where it was occasionally dominant. Schuster and Etnier (1978) and

Hilsenhoff (1987) found it to be highly tolerant of organic enrichment. Hydropsyche bidens Ross

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was collected from all sites except Panther Creek. It appeared to prefer larger rivers (Moulton and

Stewart 1996), where it was often abundant.

Eleven species of hydroptilid, or micro-, caddisflies were taken from or known to occur in

the lower Illinois River basin near the stream sites. Two species were abundant, Hydroptila ajax

Ross and H. angusta Ross. The greatest abundance of H. ajax occurred in Indian Creek, a small,

open stream. Hydroptila angusta inhabited small stream and large rivers and has been found in

abundance in light trap samples from the Ohio River (DeWalt, 1998). Another micro-caddisfly,

Mayatrichia ayama Mosely, was taken only at the Illinois River near Florence. Ross (1944) and

Moulton and Stewart (1996) describe its habitat preference as being for small-to-medium-sized,

rapid, clear streams. Although several specimens were taken at Florence, some doubt exists that

this was their origin. Small brooks run out of the bluff above this site nearby.

Leptocerid caddisflies, with 17 species, contribute the greatest species richness for

caddisflies in this study. A significant finding was that of several females of the rarely collected,

N. pavida (Hagen) at the Sangamon River, Monticello site. Ross (1944) reported this from two

collections, Monticello and Herod (southern Illinois). Oecetis inconspicua (Walker) was present at

all sites. It is perhaps the most widely distributed caddisfly species in Illinois due to its ability to

live in both lotic and lentic environments (Ross 1944). Small populations of five other Oecetis

species were take during the study. A large number of female Triaenodes melacus Ross were

taken from Panther Creek. To date this species has only been recorded from two other location in

the state, Cooper Creek near Mill Creek and it type locality of Blackman Creek near Rudement,

both in the Shawnee Hills of southern Illinois. It has been taken in low numbers from scattered

locations in AL, IN, KS, KY, MO, MS, and OH.

Cyrnellusfraterus (Banks) was the only other widespread and abundant caddisfly species.

Ross (1944) and Moulton and Stewart (1996) report it principally from large rivers, but it has been

found in smaller streams and at the shores of lakes (DeWalt, pers. obs.). Hilsenhoff (1987) rates

it as being highly tolerant of organic enrichment.

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CONCLUSIONS

Inspection of 17,889 specimens from this Illinois River basin study has demonstrated that

its EPT assemblage, as represented by light trap collections, was overwhelmingly dominated by

caddisflies. Sixty-one percent of all species and 88.3% of all individuals were caddisflies. Three

caddisfly families contributed 40 of the 67 EPT species encountered. These were the

Hydroptilidae (11 species), Hydropsychidae (12), and the Leptoceridae (17). These same families

also dominated abundance. Hydropsychid caddisflies contributed 56.6% of all individuals, while

the leptocerids added 19.4%, and the hydroptilids provided 7.9%. Moulton et al. (1993) studied

the caddisfly fauna of the Brazos River in Texas. They found 42 species occurring over an

equivalent time period. The same three families that were diverse and abundant in our study were

found to be diverse and abundant in the Brazos River. The species P. flava, H. bidens, and

several Cheumatopsyche sp. were dominant at several sites, the former two mostly in medium-to-

large rivers.

Mayflies contributed 34.3% of the EPT species collected, but only 11.3% of individuals.

Caenids provided three species and 6.6% of the abundance. Heptageniids provided 11 species and

2.9% of abundance. Stoneflies provided only 4.5% of all species (3 total) and only 0.4% of

abundance.

Species richness was greatest in Indian Creek (38 taxa). Lowest richness was found in the

La Moine River (21). Small-to-medium-sized streams tended to have more species than the largest

rivers. Richness peaked in July at nearly all sites, followed by August and June. Low richness in

June was most likely due to lower air and water temperature that prevented emergence early in that

month. EPT richness values were not significantly correlated with HBI values. The predicted

relationship would be inverse since low HBI numbers indicate greater stream health/biotic

integrity. In fact, the La Moine River at Colmar had the lowest overall EPT richness of any site,

but had one of the lowest (best) HBI scores. Several reasons may account for this lack of

relationship. EPT richness is counts every species encountered equally, so rare species have a

great impact upon it. Whereas, the HBI weights the tolerance values of taxa by their abundance.

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Additionally, for several abundant taxa (Cheumatopsyche sp., Hydroptila sp. and others) we were

forced to assign tolerance value for the genus, as no species-level tolerance values exist. Some

species within a genus may well have biologically significant differences in ecological tolerance.

These weaknesses demonstrate the need to use both taxonomic richness and a biotic index for

monitoring of stream health.

Both EPT and HBI values, calculated on adult data, should be focused on the entire

community within an emergence season. This can best occur when light trap samples are available

for several months. If this is not possible, then an early July light trap sample would be the next

best choice. We have found that an HBI score based solely on July light trap collections best

mimicked the HBI score taken across June, July, and August. Similarly, the number of EPT

found in July samples was much closer to the summer-long EPT list.

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ACKNOWLEDGMENTS

We wish to thank the INHS for providing facilities and time relief for this project. Mitch

A. Harris, of the USGS, helped secure funding and aided in the design of collection protocols.

We wish to thank D. L. Adolphson, P. J. Terrio, and K. Gao, of the USGS, and L. J. Peraino, of

the INHS, for help with light trapping of insects. The University of Illinois through the Federal

WorkStudy program provided student workers who helped collect, sort, label, and database

specimens. These students were P. Li, M. Lavin , D. Duong, B. Lopez, and L. Hernandez.

Without their help, this project would not have been feasible.

15

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in an intermittent stream in northern Texas. Annals Entomological Society of America 72:

659-666.

Wallace, J. B., J. W. Grubaugh, and M. R. Whiles. 1996. Biotic indices and stream ecosystem

processes: results from an experimental study. Ecological Applications 6:140-151.

17

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Table 2. Hilsenhoff Biotic Index (HBI) values and brief discussion of tolerance values for EPTspecies collected during summer 1997 at eight lower Illinois River basin sites.

Taxon HBI DiscussionAcentrella ampla No HBI availableBaetis intercalaris 6Fallceon quilleri No HBI availableLabiobaetis propinquus 6Paracloeodes minutus No HBI availableCaenis amica 7 for genus Caenis, none for species givenCaenis hilaris 7Caenis latipennis 7Hexagenia bilineata 6 for genus Hexagenia, none for species givenHexagenia limbata 6Pentagenia vittigera 6Heptagenia diabasia 3Heptageniaflavescens No HBI availableLeucrocuta aphrodite No HBI availableLeucrocuta maculipennis No HBI availableNixe inconspicua _No HBI availableStenacron interpunctatum 7Stenonema mexicanum 4 S. integrum is a synonym of S. mexicanumStenonema luteum No HBI availableStenonema prob. pulchellum 3_Stenonema terminatum 4Isonychia rufa 2 for genus Isonychia, none for species givenEphoron album 2 for genus Ephoron, none for species givenEphoron leukon 2Anthopotamus myops 4Perlesta decipiens 5 as Perlesta placida, a complex, containing P. decipiens,

the most common species in the region.Perlinella drymo 1Isoperla bilineata 4Helicopsyche borealis 3Ceratopsyche bronta 5Cheumatopsyche aphanta 5 for genus Cheumatopsyche, none for species givenCheumatopsyche campyla 5Cheumatopsyche lasia 5Cheumatopsyche pettiti 5Hydropsyche betteni 6Hydropsyche bidens 3Hydropsyche simulans 7Potamyia flava 5Hydroptila ajax 6 for genus Hydroptila, none for species givenHydroptila albicornis 6 __________________________

Hydroptila angusta 6Hydroptila consimilis 6_____..Hydroptila perdita 6____Hydroptila waubesiana 6

19

Table 2. Hilsenhoff Biotic Index (HBI) values and brief discussion of tolerance values for EPTspecies collected during summer 1997 at eight lower Illinois River basin sites.

Taxon HBI DiscussionMayatrichia ayama No HBI availableOrthotrichia cristata No HBI availableOxyethira pallida 3 for genus Oxyethira, none for species givenCeraclea punctata 3 for genus Ceraclea, none for species givenCeraclea tarsipunctata 3Ceraclea transversa 3Leptocerus americanus No HBI availableNectopsyche candida 3 for genus Nectopsyche, none for species givenNectopsyche diarina 3Oecetis avara 8 for genus Oecetis, none for species givenOecetis cinerascens 8Oecetis inconspicua 8Oecetis persimilis 8Triaenodes marginatus 6 for genus Triaenodes, none for species givenTriaenodes tardus 6Anabolia consocia 5 for genus Anabolia, none for species givenChimarra obscura 4 for genus Chimarra, none for species givenPhryganea sayi 8 for genus Phryganea, none for species givenCyrellus fraternus 8Neureclipsis crepuscularis 7 for genus Neureclipsis, none for species givenParanyctiophylax affinis 5 for genus Paranyctiophylax, none for species givenPolycentropus sp. 6 for genus Polycentropus, none for species given

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