Prosyrphus thompsoni, Grimaldi, 2018

Grimaldi, David A., 2018, Basal Cyclorrhapha In Amber From The Cretaceous And Tertiary (Insecta: Diptera), And Their Relationships: Brachycera In Cretaceous Amber Part Ix David A. Grimaldi, Bulletin of the American Museum of Natural History 2018 (423), pp. 1-97 : 1-97

Prosyrphus thompsoni , new species

Figures 21 , 52

DIAGNOSIS: As for genus, by monotypy.

DESCRIPTION: (male only). Body stout, compact. Head: Broad, slightly broader than thorax, faintly compressed dorsoventrally. Eye completely bare of setulae; large, occupying all of dorsal and lateral surfaces and much of venter; dorsal facets slightly larger than ventral ones, no discrete dividing line; male holoptic for entire length of frons. Frons obscured (presence/ absence of median furrow, interfrontal and fronto-orbital setae not determinable). Ocelli on low tubercle, with two small pairs of stiff ocellar setae. Vertical setae absent; postocular setae fine, small; occiput faintly concave, with scattered fine setulae. Face relatively broad, ~0.3× width of head; bare, slightly swollen in middle; anterior tentorial pits deep, vertical and slitlike, close to eye margin. Oral cavity small, entirely ventral; vibrissa and genal setae absent. Antenna: Scape small, bare, slightly asymmetrical; pedicel asymmetrical, with tonguelike lobe inserted into mesal surface of basal flagellomere; arista dorsal; basal flagellomere reniform; arista with two minute articles at base, apical article long, flagellate, tapered to very fine apex, completely bare of micropubescence. Mouthparts: Clypeus minute; oval; isolated, not articulating with labrum; palp small, slender; proboscis, small, short, slender; labrum slender; labellum small, arely wider than rest of proboscis.

Thorax: Short, broad, deep in lateral view; scutum rounded but not arched. Acrostichals numerous, scattered, not in rows. Dorsocentral macrosetae present, in 2 prescutellar pairs, none in serial rows. Macrosetae: 2 supraalar; 5 notopleural; 4 pairs of scutellars, longest ones near center, disk of scutellum with setulae. Wing: Broad, length/width 2.0, tapered apicad; hyaline, slightly darkened between apices of Sc and R 1; membrane with dense, very fine microtrichia, less dense in cell Sc; pterostigma absent. Prehumeral costal seta(e) small, large macrosetae absent; vein C with minute spinules; end of C not visible (wing tips lost at surface of amber); Sc long, ~0.6× length of wing; R 1 long, running close to base of Sc, slightly diverging apicad; sc-r appears absent; R 2+3 straight, base weak; R 4+5 straight; spurious vein absent; cell dm large, cleaver shaped; cell rm long, r-m at same level as apex of Sc; cell bm narrow; crossvein dm-cu close to wing margin, separated by distance ¾ length of dm-cu; M 1 -M 2 forked, tip of M 1 not reaching wing margin; tip of CuA 1 not reaching wing margin; CuA 2 curved, A 1 straight; cell cup large, much longer than apical vein; anal lobe large, alula relatively small. Halter stem slender.

Legs: Setose, relatively short, slender; femora longer than respective tibia, profemur with ventral row ~7 long setae, setal lengths about equal to femur width. Mesotibia with short, stout ventroapical spur. Basitarsomeres longest of all tarsomeres; pulvillus ~0.7× length of claw; empodium not observable (perhaps minute); claw ~0.5× length of tarsomere 5.

Abdomen: Short, stout; anterior 4 tergites large, with short, scattered setulae, laterally curved but not contacting sternites (pleural membrane exposed). Five large sternites visible, anterior and posterior margins in contact; with short, scattered setulae. Male Terminalia: Segments 6, 7, and 8 asymmetrical, ventroflexed; sternites 5 and 6 exposed dorsally; sternite 8 bulbous, terminal; epandrium triangular, shifted to left; surstyli large, heavily setose; cerci symmetrical, setose, hidden beneath sternite 8, point forward.

Female Terminalia: unknown.

SPECIMENS EXAMINED: Holotype, male AMNH Bu-SE03 The specimen is in beautiful condition, very well preserved, and virtually complete (missing only the tips of the wings).

ETYMOLOGY: Patronym for F.C. Thompson, for his many contributions to the systematics of Syrphidae and Diptera in general.

Figures

FIG. 21. Prosyrphus thompsoni, n. gen., n. sp. (Syrphoidea), male holotype in Burmese amber, AMNH Bu-SE03. A. Left ventrolateral habitus. B. Right dorsolateral habitus. C. Anterior half of body. D. Detail of male terminalia, left side.

FIG. 52. Prosyrphus thompsoni, n. gen., n. sp. (Syrphoidea), male holotype in Burmese amber, AMNH Bu-SE03. A. Head, ventral view. B. Thorax, dorsolateral view. C. Male terminalia, left ventrolateral view. D. Wing.