Gracilomyia wit, Grimaldi, 2016

Grimaldi, David A., 2016, Diverse Orthorrhaphan Flies (Insecta: Diptera: Brachycera) In Amber From The Cretaceous Of Myanmar: Brachycera In Cretaceous Amber, Part Vii David A. Grimaldi, Bulletin of the American Museum of Natural History 2016 (408), pp. 1-132 : 79-81

Gracilomyia wit , new species

Figures 27 , 59

DIAGNOSIS: As for genus, by monotypy.

DESCRIPTION: Based on unique female. A relatively large, slender, and elongate fly with long, slender legs. Body length 7.51 mm; thorax length 2.58 mm; thorax width 1.00 mm; abdomen length 3.77 mm; wing length 4.81 mm; antennal length 0.61 mm. Head: Subspherical, slightly compressed dorsoventrally, slightly broader than thorax. Frons dark, bare; ocellar triangle slightly raised above frons, ocelli forming equilateral triangle, anterior ocellus facing forward. Face, beneath antennal insertions, short. Occiput convex. Eye: Large, completely bare, no differentiation of facets; in lateral view eye occupying most of head, occiput slightly exposed posteriorly; in dorsal view eyes widely separated, ca. 2× width of ocellar triangle. Antenna: Stylate, with 4 flagellar articles. Bases of antennae close, touching. Scape and pedicel small, shorter and narrower than basal flagellomere; flagellomere 1 cylindrical, with ca. 0.3× the length; flagellomere 2, 3 minute, 3 is short, ringlike; flagellomere 4 long, slender, stylate (not aristate or flagellate), longer than rest of antenna, apex with 2–3 fine, stiff setulae, no minute apical style. Mouthparts: Labellum large, flattened laterally (number of pseudotracheae not observable); number of palpomeres not observable (presumably 2), apical palpomere fairly broad in lateral view. Other mouthparts, clypeus not observable (if clypeus bulging, then very slightly). Thorax: Narrow in dorsal view, slightly narrower than abdomen; deep in lateral view, not oblique (ventralmost point of katepisternum is beneath level of anepisternal cleft). Antepronotum very large, collarlike, glabrous, dorsally shielding long, thin neck. Postpronotal lobes moderately projecting laterally. Scutum and scutellum with fine, short, decumbent setulae; thorax without macrosetae or long pilosity; scutellum longer than wide, no spines; proscutellum very small. Wing: Long, slender, W/L 0.30, apex narrow, not rounded; vein C circumambient. Sc long, 0.6× wing length; R 1 long, 0.73× wing length; Sc and R 1 close, parallel; presence/absence sc-r not observable; faint pterostigma between apices of R 1 and Sc. Rs short; R close and parallel to R 1; fork of R 4+5 relatively short, slightly asymmetrical (R 4 slightly longer and more curved), length of fork equal to length of R 4+5 stem; apex of R 4 distinctively ending at tip of wing. Cell d large, broad, crossvein r-m near base of cell. Two short M veins present, M 1 and M 2, lengths less than length of cell d. A 1 very short, complete, meets wing margin at midlength of wing; A 2 very short. Anal lobe and alula very narrow. Legs: Coxae slender; mesocoxa contacting thorax just at its base, largely free from katepisternum and meron; metacoxa well separated from mesocoxa, with well-developed knob in middle of anterior surface. Leg segments: femur = tibia> basitarsomere> combined length of other tarsomeres. Tibial spurs 1-2-2; all tibial spurs fine; protibial spur short (length less than width of tibia); lengths of meso- and metatibial spurs slightly greater than width of tibia. Legs without macrosetae. Pretarsi lost or largely obscured, pulvilli appear to be present; empodium ambiguous (either lost, very small, or setiform). Abdomen: Longer than thorax and head combined. Tergites well developed, 9 tergites visible, with short, fine, decumbent setae; tergite 1–8 wrapping laterally and overlapping with lateral margins of sternites (which are also large, well developed), no lateral membrane exposed. Sternites 1, 2 narrower than segment 3 in dorsal view (ca. 0.7× the width); 0.5× depth of segment 3 in lateral view—almost petiolate. Tergite 9 small, almost enclosed by tergite 8. Apex of abdomen opening ventrally. Cercus 2-segmented, apical halves of apical cercomeres shaved off at amber surface; basal cercomere small, ringlike, sclerotized, enclosed by tergite 9, ventral portion does not appear to have small lobe.

2+3

TYPES: Holotype, female, AMNH Bu-SE14.

ETYMOLOGY: Acronym for “what is this?” Treated as a noun in apposition.

COMMENTS: Piece containing the holotype is 5 × 9 × 13 mm, trimmed from a larger cabochen, with flattened surfaces for viewing the dorsal and left lateral surfaces close to the fly. The amber has a thick suspension of fine bubbles, which, along with some fine circular fractures around portions of the head and thorax, obscure some structures. Of the three tarsi that are preserved, two are curled toward the body, obscuring the pretarsi. Only the left protarsus is visible (dorsally), and light must be repeatedly moved to obtain views of the pretarsus. It is likely that the empodium is not pulvilliform. The fly is virtually complete; apices of four legs and portion of the distal cercomeres were lost at the surface of the amber.

Figures

FIG. 27. Gracilomyia wit, new genus and species (unplaced to family), AMNH Bu-SE14, holotype. A. Wing. B. Antenna. C. Head and anterior portion of thorax, dorsal view. D. Female terminalia, posterior view. The apices of distal cercomeres were lost at surface of the amber.

FIG. 59. Gracilomyia wit, new genus and species (unplaced to family), holotype AMNH Bu-SE14. A. Habitus, dorsal. B. Habitus, lateral. C. Head, left lateral. D. Abdomen and wings, dorsal.