Cratomyia mimetica, 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 : 8-11

Cratomyia mimetica , new species

Figures 1 , 2 , 33

DIAGNOSIS: Like C. macrorrhyncha (Crato Formation: Brazil) with short R 4 -R 5 fork, long, narrow m 3 cell, and short M 1+2 stem. Distinguished from that species by: M 1 slightly sinuous with tip slightly upturned (vs. arched downward), cell d slightly narrowed distally (vs. uniform width), cell m 3 very narrow, W/L 0.11 (vs. 0.22), anal lobe well developed. Distinguished from the other species in Burmese amber, Linguatormyia teletacta Grimaldi , by longer, narrower cell d, presence of M 1+2 stem, narrower wing (W/L 0.36, vs. 0.41), much shorter basal palpomere (>5× length of apical palpomere in Linguatormyia ); palpomeres nearly equal in length in C. mimetica ; and by wasplike abdomen (vs. short, dorsoventrally flattened abdomen).

DESCRIPTION: Unique female, extraordinarily well preserved, with color patterns distinct (figs. 1, 2). Light yellowish body with bold, black markings, patterns as described below under head, thorax, abdomen. No macrosetae on body, only fine, short, decumbent setae and setulae. Rather stout-bodied fly with thorax compact, abdomen relatively large. Head width 2.16 mm, thorax length 1.88 mm, wing length 4.84 mm, abdomen length 4.49 mm. Head: Slightly broader than thorax, compressed/slightly flattened dorsoventrally. Dark areas include occiput, vertex, median strip on frons, around bases of antennae, most of face, at least base of proboscis (apical portion lost), at least base of antenna (apical portion lost), tips of palps. All other areas very light yellow. Frons broad, width slightly less than width of eyes; flat, setulose. Ocelli light, small; on small mound slightly raised above frons, forming equilateral triangle, situated on vertex of head. Face concave, with deep paraclypeal sulci; clypeus bulbous. Hypostomal bridge complete (not interrupted medially); ventral surface of head just below mouthparts with long, fine, light setae. Occiput gently concave. Eye: Large, bare, no differentiation of facets, color light; reniform in shape dorsally (modest emargination near middle of margin with frons); broadest surface is frontally. Antenna: Bases close but distinctly separate, not contacting; scape, pedicel, and basal three flagellomeres preserved, all uniform in size and shape (short cylindrical), without long, fine setae. Mouthparts: Proboscis long, thin, projecting forward (only base preserved, most is lost at surface). Palp 2-segmented, basal palpomere slightly longer than apical one, apical palpomere slightly expanded at apex; devoid of long, fine setae. Thorax: Short, relatively deep, without pilosity except on laterotergite. Coloration: Black markings on middle portion of scutum, incomplete stripes lateral to this (broader posterior to transverse suture); all of katepisternum, ventral half of anepisternum, meron; all of laterotergite; portion of postpronotal lobe and preepisternum; dorsal half of metacoxa, most of legs (bases of meso- and metafemur light, as are femoral-tibial articulations). All other areas of thorax light, including scutellum and halter. Scutum short, rounded in profile; transverse suture well developed but barely dorsal. Pleura largely vertical, not oblique, with ventralmost portion of katepisternum beneath level of anepimeral cleft. Antepronotum quite small; postpronotum, postpronotal lobe, and preepisternum ventrally positioned, not at anterior end of thorax. Wing: Relatively narrow, W/L 0.36. Veins C, R 1, R 2+3 thick, dark; C ending at tip of M 1. Entire area between Sc and R 1 darkened, even at base. Sc complete, long, 0.62× wing length; R 1 0.76× wing length, close and parallel to Sc and R 2+3; R 2+3 0.81× wing length. Rs very short; fork of R 4 -R 5 very short, 0.3× entire length of R 4+5. M 1 not arched, slightly sinuous, tip ending at apex of wing, M 2 distinctly incomplete; M 1 and M 2 joined to short stem (M 1+2) (vs. directly to cell d). Cell m 3 long, very narrow, W/L 0.11. Cells br, bm of equal length; cell cup long, closed; apex of CuA 1 +A 1 meeting wing margin well past midpoint of wing (0.61× wing length). A 2 well developed, apically evanescent; anal lobe well developed, alula barely observable, upper calyp- ter small. Legs: Pro- and mesocoxa light; metacoxa dorsally dark; mesocoxa only slightly closer to metacoxa than to procoxa, not contacting either one; metacoxa with well-developed knob/ tubercle on anterior surface. Legs without macrosetae; with only dense, short, decumbent setae/ setulae. Leg segment lengths: tibia> femur> basitarsomere> combined length of other (distal) tarsomeres. Tibial spurs 0-2-2; spurs relatively robust, shorter than apical width of tibia. Pretarsus with claws well developed, pulvilli shorter than claw; empodium pulvilliform, about same size as pulvillus. Abdomen: Large, length 1.3× that of head + thorax, width about equal to thorax in dorsal view, deeper than thorax in lateral view. Wasplike, with narrowed waist and apex: tergite 2 0.5× width of t3, anterior portion of t2 constricted; in lateral view t2 lower than other tergites but rounded, slightly nodelike. Markings: Tergites 2–7 with middle portions dark, t4 with dark hourglass shape, t5 and t6 with dark stripes forming light posterior spots. Dark lateral spots on tergites 4–6. Tergite 7 with 4 light spots on posterior margin; all of t8 dark. Tergites overlapping sternites laterally, abdominal pleural membrane not exposed. Sternites 3–5 with dark median area. Terminalia obscured by bubbles, largely retracted into sternite/tergite 8.

TYPE: Holotype, female, AMNH Bu-SD1.

ETYMOLOGY: From Greek, mimos (“imitator, actor”), in reference to the wasplike color patterning and body shape.

COMMENTS: Preservation of the fly is superb; the only portions lost at the surface of the amber are parts of the antennae and proboscis and apical half of the right wing. The fly is in a yellow, very clear cabochen of amber 4 × 5 × 15 mm.

This may be the earliest-known occurrence in the fossil record of aposematic mimicry, specifically of an aculeate (stinging) wasp as the model (figs. 1, 2). Diverse families of aculeates occur in Burmese amber, some of them abundant and speciose, such as ants ( Formicidae ) and apoids ( Crabronidae and relatives). The markings on Cratomyia mimetica , however, strikingly resemble Vespidae , particularly of the abdomen. The constriction between abdominal segments one and two and the narrowed dark markings at the base of the abdomen (along with the light bulb of the halter) lend appearance to a wasp petiole. Further, the very dark, thick costal vein and dark membrane between Sc and R 1 must have resembled vespid wings when folded over the abdomen. Vespidae occur in Burmese amber ( Perrard et al., 2016), but these are stem-group vespids and the coloration patterns of the specimens found thus far are not preserved.

Figures

FIG. 1. Cratomyia mimetica, new species (Zhangsolvidae), reconstruction of lateral habitus, without wing; coloration as preserved. Based on holotype specimen, AMNH Bu-SD01.

FIG. 2. Cratomyia mimetica, new species (Zhangsolvidae), reconstruction of dorsal habitus based on holotype. The preserved coloration pattern resembles that of stinging wasps, Vespidae.

FIG. 33. Cratomyia mimetica, new species (Zhangsolvidae), holotype AMNH Bu-SE01. A. Left habitus. B. Right habitus. C. Head and thorax.