A Fossil Horsefly (Diptera: Tabanidae) in Dominican AmberAuthor(s): Robert S. Lane, George O. Poinar, Jr. and G. B. FairchildSource: The Florida Entomologist, Vol. 71, No. 4 (Dec., 1988), pp. 593-596Published by: Florida Entomological SocietyStable URL: http://www.jstor.org/stable/3495018 .

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Lane et al.: Fossil Horsefly 593

A FOSSIL HORSEFLY (DIPTERA: TABANIDAE) IN DOMINICAN AMBER

ROBERT S. LANE AND GEORGE 0. POINAR, JR.

Department of Entomological Sciences, University of California Berkeley, California 94720, USA

G. B. FAIRCHILD Florida Department of Agriculture and Consumer Services

Gainesville, Florida 32602, USA

ABSTRACT

A fossil horsefly, Stenotabanus brodzinskyi n.sp., embedded in a piece of Dominican amber estimated to be 25 to 40 million years old is described and compared to extant members of the genus known from Hispaniola.

RESUMEN

Un tabanido f6sil, Stenotabanus brodzinskyi n.sp., incrustado en una pieza de ambar dominicano, cuya edad estimada es 25 a 40 millones de anios, es descrito y comparado con congeneres vivientes conocidos en La Espafiola.

Eight species and 1 infraspecific taxon of fossil Tabanidae (Diptera) representing 4 genera (Chrysops, Haematopota, Silvius, Tabanus) have been described worldwide (see review by Moucha 1972 and Stuckenberg 1975). These include 3 species (Silvius, 1; Tabanus, 2) from the New World that were obtained from Miocene deposits of Floris- sant, Colorado, U.S.A. (Cockerell 1909, 1917, Melander 1946). Here we describe from Dominican amber the first fossil member of the genus Stenotabanus and discuss its relationship to extant members of the genus from Hispaniola.

DESCRIPTION

The fly is embedded in a piece of amber approximately 15.1 mm x 9.3 mm x 8.8 mm. It is from an unspecified amber mine in the Cordillera Septentrional mountain range in northern Dominican Republic. Amber from several mines in this region have been estimated to be 25 to 40 million years old (Lambert et al. 1985) corresponding to early Miocene and late Eocene.

Important specific characters of Tabanidae include thoracic and abdominal ground colors and any overlying pubescent coloration. Since preservation of this fly in amber doubtless precluded accurate assessment of these character states, we present here as complete a description as possible with the caveat that the colors reported may not have reflected those of the fly in life. Indeed, most of the body of this specimen was colored various shades of orange-brown to dark brown with a golden tinge or metallic-like luster which seemed to reflect, at least in part, the orange color of the amber itself.

The format for the ensuing description follows that of Fairchild (1980), who described as new 3 species of Stenotabanus and 1 species of Tabanus from the Dominican Republic and presented a key to all 29 recognized Hispaniolan species. Terminology follows Fair- child (1980) and McAlpine (1981).

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594 Florida Entomologist 71(4) December, 1988

Stenotabanus brodzinskyi sp.nov. (Figs. 1-4)

Diagnosis: A small orange-brown/brown species having hyaline wings, an unstriped mesonotum, and a narrow, convergent frons.

Female: Length of body 9.0 mm, of right wing 7.3 mm. Eyes bare, golden brown without evident banding. Postorbital hairs long, black medianly and shorter, pale sub- medianly and laterally. Frons narrowed below, ca. 5.4x taller than basal width, with index of divergence (width at vertex/width at base) 2.1, golden pollinose with scattered, long dark hairs throughout (absent on basal callus), these hairs somewhat denser toward vertex. Basal callus golden apically, brown basally, shape as in Fig. 2. Median callus golden, elongate, thin, reaching ca. 0.7 height of frons, connected to basal callus. Ocellar tubercle obscured by debris, dark brown; ocelli inconspicuous, only vestiges of anterior ocellus visible. Vertex (Fig. 2) poorly discernible. Subcallus brown, predominantly bare. Frontoclypeus brown with sparse, long dark hairs; genae slightly darker brown, par- tially covered with pale pollinosity, short, scattered dark hairs and long pale hairs, the latter readily discernible in photographs (Fig. 4) but not by microscopic examination. Antennae with scape, pedicel, and basal plate of 3rd segment dark orange-brown, the style dark brown; scape, pedicel and dorsal process of basal plate black-haired. Left antenna 1.32 mm long, with 3rd segment ca. 2.3x longer than length of scape and pedicel combined. Palpi orange-brown, slender, elongate, shape as in Fig. 4, with apical seg- ment ca. 6x longer than greatest diameter in lateral view and beset with numerous black hairs on all surfaces; basal palpal segment clothed with numerous long, pale hairs and scattered, long black hairs. Proboscis orange-brown, length subequal to that of palpi but shorter than height of head.

Mesonotum metallic orange-brown to golden without longitudinal stripes, moder- ately clothed with short, dark recumbent hairs medianly and scattered, longer erect dark hairs anteriorly, anterolaterally and laterally. Scutellum and prescutellum bare except for scattered long dark hairs laterally on former. Notopleuron heavily clothed with long dark hairs. Pleura ground color dark brown, covered in part by golden pol- linosity appearing as a metallic sheen; sparsely pale-haired except for katatergite, the latter densely covered with long pale hairs. Knobs of halteres dark brown, the stems light brown. Right wing 7.3 mm long, hyaline except for a faint cloud apically at furca- tion (junction of R4 and R5 veins) that appears to be an artifact of preservation; venation normal, 1st posterior cell open widely, lacking appendix on 3rd vein; stigma dark brown; slightly more than apical 1/2 of left wing missing. Basicosta sharply pointed, bare api- cally, with sparse setulae basally. Costa, subcosta, and R1 clothed with dark, robust, short setae. Coxae and femora brown, covered partly with golden pollinosity presenting as a metallic sheen, dark-haired with some pale hairs ventrally. Tibiae and tarsi orange- brown to dark brown, black-haired; fore- and hindtibiae without apical spurs, midtibiae with 2 strong spurs apically; tarsi with paired claws subequal in length.

Abdomen orange-brown to dark brown in ground color with posterior sternites and tergites darkest, predominantly dark-haired, lacking conspicuous pubescent color pat- terns.

Holotype female. The fly is named after its discoverer, J. Brodzinsky, of Santo Domingo, Dominican Republic. The piece of amber containing the fly described here is currently owned by J. Brodzinsky and is now being held in the amber collection of G. 0. Poinar, Jr., at the University of California, Berkeley (accession number D-7-101).

DISCUSSION

The fossil Stenotabanus possesses characteristics of the subfamily Tabaninae and the tribe Diachlorini listed by Mackerras (1954). Additionally, it meets the generic

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Lane et al.: Fossil Horsefly 595

Figs. 1-4. Female Stenotabanus brodzinskyi n.sp. in Dominican amber: 1-Dorsolat- eral view of entire fly; 2-Anterior view of head showing details of eyes, subeallus, frons, and vertex in part; 3-Ventral view of antennae; 4-Ventrolateral view of head displaying palpus and proboscis.

criteria for Stenotabanus presented by Fairchild (1980, p. 168), which include the ab- sence of strong setae on the basicosta and the presence of a tubercle at the vertex. Fairchild (1980) recognized 3 groups of Hispaniolan Stenotabanus, namely, the subgenus Aegialomyia and the brunettii and fenestra groups consisting of 2, 3, and 3 species, respectively. Of these 8 species, 7 are endemic to the Dominican Republic and 1 is widespread in the Greater Antilles.

The fly described here does not belong to the subgenus Aegialomyia because the height of the frons is ca. 5.4 times its basal width (vs. less than 4 times as high as basal width in Aegialomyia) and it has a prominent tubercle at the vertex (vs. small tubercle at vertex in Aegialomyia). On the other hand, its clear wings and seemingly unstriped mesonotum warrant tentative placement of this fly in the fenestra group which contains S. fenestra Williston, S. marcanoi Fairchild, and S. hispaniolae Bequaert. In Fairchild (1980), it keys out to S. marcanoi from which it differs by its smaller size (body 9 mm long vs. 11 mm in marcanoi); the apparent absence of white hairs on the frontoclypeus, legs and sternites; lack of a short appendix at the fork of the 3rd vein; and having palpi and proboscis subequal in length (vs. proboscis about twice the length of the palpi in marcanoi).

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596 Florida Entomologist 71(4) December, 1988

The published fossil record for Tabanidae reviewed by Moucha (1972) may be up- dated as follows: Chrysops is represented by 1 species from the Eocene of France; Silvius by 1 species from the Miocene of North America; Tabanus by 1 species from the upper Oligocene and 1 subspecies from the upper Pliocene of Germany, 2 species from the Miocene of North America, and probably 1 species from the Oligocene of the Isle of Wight; Haemtopota by 1 species from upper Eocene Baltic amber; and Stenotabanus by 1 species from early Miocene-late Eocene Dominican amber (Stucken- berg 1975, present study). In addition the Baltic amber Silvius laticornis, though osten- sibly a chrysopsine, was misplaced generically by Hennig (1967) and needs to be reevaluated (Stuckenberg 1975). Thus, the discovery of the Dominican amber Stenotabanus brings to 9 the number of fossil tabanid species reported in the literature. Moreover, this fly represents the first fossil member of the tribe Diachlorini and of the genus Stenotabanus to be described. Unfortunately, a clue to the probable feeding habits of this tabanid cannot be found among the 3 related Dominican species of Stenotabanus assigned to the fenestra group inasmuch as their biologies are unknown (Fairchild 1980).

Two of us (G.B.F. and R.S.L.) are preparing for publication the description of another female Stenotabanus embedded in a piece of Dominican amber. This specimen, which was obtained from the same montane region as our fly, represents another unde- scribed species.

ACKNOWLEDGMENTS

We thank W. W. Middlekauff, University of California, Berkeley (UCB), for review- ing the manuscript, and J. Santiago-Blay (UCB) for translating the English abstract into Spanish. J. Brodzinsky, Santo Domingo, Dominican Republic, is gratefully acknowl- edged for lending us the piece of amber for study.

REFERENCES CITED

COCKERELL, T. D. A. 1909. Fossil insects from Florissant, Colorado. Bull. Amer. Mus. Nat. Hist. 26: 67-76.

COCKERELL, T. D. A. 1917. Some American fossil insects. Proc. U.S. Nat. Mus. Washington 51: 89-106.

FAIRCHILD, G. B. 1980. Tabanidae (Diptera) from the Dominican Republic. Florida Entomol. 63: 166-188.

HENNIG, W. 1967. Die sogenannten 'niederen Brachycera' im Baltischen Bernstein (Diptera: Fam. Xylophagidae, Xylomyidae, Rhagionidae, Tabanidae). Stuttg. Beitr. Naturk. 174: 51 pp.

LAMBERT, J. B., J. S. FRYE, AND G. 0. POINAR, JR. 1985. Amber from the Domini- can Republic: analysis by nuclear magnetic resonance spectroscopy. Ar- chaeometry 27: 43-51.

MACKERRAS, I. M. 1954. The classification and distribution of Tabanidae (Diptera). I. General review. Aust. J. Zool. 2: 431-454.

McALPINE, J. F. 1981. Morphology and terminology-adults. Pages 9-63 in McAl- pine, J. F. et al., Manual of Nearctic Diptera. Volume 1. Res. Branch Agric. Canada Monograph No. 27.

MELANDER, A. L. 1946. Some fossil Diptera from Florissant, Colorado. Psyche 53: 4349.

MOUCHA, J. 1972. Prehled fosilnich druhu ovadovitych (Insecta: Tabanidae). Cas. Nar. muz. odd. Prirod. 141: 28-29.

STUCKENBERG, B. R. 1975. New fossil species of Phlebotomus and Haematopota in Baltic amber (Diptera: Psychodidae, Tabanidae). Ann. Natal Mus. 22: 455-464.

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