Tethepomyia zigrasi Grimaldi & Arillo

Grimaldi, David A., Arillo, Antonio, Cumming, Jeffrey M. & Hauser, Martin, 2011, Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa, ZooKeys 148, pp. 293-332 : 319-321

Tethepomyia zigrasi Grimaldi & Arillo sp. n. Fig. 10

Diagnosis.

Distinguished from the other two species of the genus, which are known only from males ( Tethepomyia thauma Grimaldi and Cumming: New Jersey amber; and Tethepomyia buruhandi Grimaldi and Arillo: Spanish amber), by the following: thickened costal and Rs veins, bases of M and Cu complete; dorsoventral differentiation of eye facets (in female, undoubtedly more differentiated in males); U-shaped basal flagellomere large, pedicel small, indistinct. Known only from female.

Description.

Body length (tip of basal flagellomere to posterior-most surface of tergite VIII) 2.15 mm. HEAD: Hemispherical in female; eyes very large, covering most of head, only small strip of gena exposed [view of face and frons not visible]. Dorsal eyes facets approximately 0.5 × diameter of ventral facet; eye completely bare, no interfacetal setulae. No setae apparent on gena or frons. Ocelli possibly on small tubercles - small, digitate lobes in this area [but details obscure]. Antenna with large, crescent-shaped basal flagellomere; pedicel apparently small [indistinct]. Proboscis and palps not visible [ventral surface of head covered with bubble]. Posterior surface of head evenly and shallowly concave. Cervical region long; head not adpressed to pronotum.

Thorax: Small and short, L = 0.55 mm, with scutum arched, posterior half long and sloped; scutum and scutellum devoid of acrostichals or setae. Scutellum short, length ca. 0.20 × that of scutum; posterior margin flat and slightly concave, not acute. Legs bare, devoid of setae or setulae; with femora slightly swollen in middle. Fore and mid coxae adjacent, hind tibia with coxal-trochanteral articulation facing anteriad (hind legs apparently held forward). Tibiae long and slender (slightly shorter than respective femur). Metatibia slightly bowed, as if to fit tightly against ventral surface of femur. Tarsi short, with basitarsomere only slightly longer than tarsomere 2 [most tarsomeres obscured by layer of air). Halter long; knob large, length of stem approximately 2.2 × greatest diameter of knob; stem without setae. Forewing with reduced venation; veins extremely light (particularly M and Cu); microtrichia of forewing either absent or so microscopic as to not be visible; no costal spinules or fringe of fine setulae on posterior margin of wing. Vein C short, extended to only ca. 0.6 × length of wing, sclerotized, swollen towards apex; apex of R1 fused with swollen portion of C. Rs thick, width slightly increased apicad; vein incomplete, not reaching wing margin/tip. Vein M faint, complete, tip evanescent and not reaching wing margin. Vein CuA faint, with short fork CuA1-CuA2 (length of fork 0.7 × length of stem); branches of fork curved towards anal region. What appears as deep fold (CuP?) parallel and posterior to stem of CuA. Faint, short vein A at base of posterior portion of wing; anal lobe and alula not present.

Abdomen: Tergites and sternites well developed, sclerotized; segments I - VI short (I longest), tergite VII long, sclerotized, length approximately equal to that of tII through tVI, with deeply incised membranous region basally, dorsal and lateral surfaces concave. Sternite VII very large, lobe-like, suspended beneath abdomen; apex pointed, bearing three short, sharp spines. Base of tVII apparently articulating with apex of tVI; tVII+VIII formed into a curved, sclerotized, sharp ovipositor-like structure, with a small, sharp, sclerotized spine at tip. Spine at tip of abdomen/oviscapt (sts IX) apparently interdigitating between three spines of sVII.

Type.

Holotype, Female: Myanmar, Kachin State, Early Cenomanian. Specimen is in excellent condition and is in the private collection of James Zigras.

Etymology.

Patronym for James Zigras, for allowing preparation and study of this remarkable specimen.

Discussion.

Tethepomyia zigrasi sp. n. appears to be a sister group to Tethepomyia buruhandi + thauma, from Spanish and New Jersey ambers, respectively. Tethepomyia zigrasi retains the bases of M, Rs, and Cu, which the other two species have lost. It shares with Tethepomyia buruhandi and Tethepomyia thauma many losses: of the antennal stylus, tibial spurs, crossvein r-m, veins R2+3 and R4+5, costal vestiture, fringe of marginal setulae on the wing, as well as the reduction of vein C.

With little question the oviscapt of Tethepomyia zigrasi is a hypodermic-like ( “aculeus”) structure, probably used for injecting its eggs into hosts. It was probably a parasitoid. An oviscapt of similar specialization has sporadically evolved in Diptera . It occurs in a few Phoridae (e.g., Apocephalus ), all Pipunculidae , and within the Schizophora in some Conopidae (e.g., Stylogaster ), most Tephritoidea , all Cryptochaetidae , and probably other families. The trait appears to have evolved most often in parasitoid groups (all those listed above except tephritoids). Most tephritoids inject their eggs into fruits or stems, though a few (like Pyrgotidae ) are parasitoids. Fine structure of the injecting oviscapt reveals its convergent development: what is labelled as the “ovipositor” in Pipunculidae (Hardy, 1989: 747) is probably a sclerotized, spine-like derivative of the cercus. In Cryptochaetidae the syringe-like oviscapt is sternite VIII; in Tephritoidea the oviscapt is a telescoping structure composed of segments 7-9. Interestingly, Tethepomyia has a suite of other convergent features similar to those of parasitoid families. Like Pipunculidae , Tethepomyiidae possesse large eyes; like Pipunculidae and Cryptochaetidae the family has large pulvilli; and like Cryptochaetidae the basal flagellomere is enlarged and the arista minute to lost. These are probably functionally correlated features.