Archosolva sulcata, 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 : 16-19

Archosolva sulcata , new species

Figures 5 , 6D , 36

DIAGNOSIS: Apical flagellomere long, though not slender. Distinguished from other Burmese amber xylomyids by the very broad wing (W/L 0.46), stout m cell, short R 4 -R 5 fork, and the vertical fossa beneath the wing base (apparently for receiving the mesofemur).

DESCRIPTION: Based on unique female. Body rather stout and dorsoventrally somewhat compressed. Original coloration well preserved: face, frons, antennal flagella, occiput, scutum, and tergites light to dark brown, lobe posterior to transverses suture is darker, each trochanter with blackish-brown ventral spot; scutellum, halter, pleura, legs, sternites, and mouthparts light yellowish. Body length 4.39 mm (excluding antennae); thorax length 1.57 mm; wing length 3.22 mm; abdomen length 2.09 mm. Head: Broader than thorax; short, compressed anteroposteriad, broad frontally. Frons relatively narrow, width approximately equal to 4× diameter of eye facets. Face concave, clypeus small and swollen. Ocelli: only anterior one preserved. Eye: Relatively large, occupying most of head surface in lateral, frontal, and dorsal views, broadest surface is frontally. Eye completely bare, facets not differentiated. Antenna: Submoniliform, with 8 flagellomeres evenly tapered from broad basal one to narrow apical flagellomere, latter with minute apical style (flagellum laterally compressed in unique specimen). Flagellomere lengths: 1> 8> 7> 2–6. Scape and pedicel small, narrow; antennal sockets very close, situated in ventral half of frons. Mouthparts: Palp 2-segmented, basal palpomere small, narrow, ringlike; apical one large, subcircular, laterally flattened. Proboscis short, only labellum exposed; labellum large, fleshy, laterally flattened. Thorax: Right side of thorax well preserved; left side distorted and damaged. Dorsum of scutum, scutellum, portion of anepisternum with dense, very fine, setigerous punctation; punctation sparse on pleura; no macrosetae or long pilosity; patch of longer, fine setulae on laterotergite. Transverse suture deeply impressed laterally and dorsally, curved posteriad on scutum, nearly meeting in middle. Pleura below wing base with vertical fossa, width equal to that of mesofemur (appears to have received femur). Scutellum without spines, this area of thorax poorly preserved. Pleura largely oblique (vs. vertical), with ventralmost portion of katepisternum slightly posterior to level of anepimeral cleft. Wing: Short, broad, W/L 0.46, veins well developed, all well sclerotized, including base of M (which is very thin); R 1 and R 4+5 particularly thick. Minute setulae on vein R 1 only. Vein C ends slightly past apex of R 5. No pterostigma. Sc complete, ca. 0.55× wing length; R 1 0.65× wing length, close and parallel to Sc; Rs very short, less sclerotized than rest of R, without thickened node; R 2+3 short, slightly divergent from R 1; fork of R 4 -R 5 slightly asymmetrical, R 4 0.80× length of R 5; fork short, 0.38× total length of R 4+5. Crossvein r-m close to base of cell d, M veins connected to apex of cell d, crossvein m-cu present; M 1, M 2 parallel; cell m stout, W/L 0.63; vein M 3 +CuA 1 relatively long. Cell d long and narrow, W/L 0.32; cells br and bm of equal length, bm twice the width of br. Vein A 1 meeting CuA 2, cell cup closed. Vein A 2 short; anal lobe well developed, but alula small. Legs: Length moderate. Coxae robust, meso- and metacoxae meeting, distant from procoxa. Relative lengths of leg segments: Femur> tibia> basitarsomere> combined lengths tarsomeres 2–5. Tibial spurs 0-2-1; spurs very thin, lengths about equal to apical width of tibiae. No spinules on ventral surface of hind femur. Pretarsus with well-developed simple claws; pulvilli small, ca 0.5× length of claw; empo- dium pulvilliform, short and broad. Abdomen: Slightly longer than thorax, broad and stout at base, width tapered to narrow apex; dorsoventrally flattened; tergites not well preserved, natural margins difficult to discern, t2–5 apparently with transverse sulci; t1 apparently with membranous area. Cercus 2-segmented, basal cercomere slightly longer than apical one; t10 small, lying between bases. Sternites well developed but not meeting tergites laterally, abdominal pleural membrane well exposed.

TYPE: Holotype, female, JZC Bu-208.

ETYMOLOGY: In reference to the thoracic sulcus, which apparently accomodates the mesofemur when it is raised.

COMMENTS: Specimen is in a small, irregular piece 3 × 5 × 10 mm, with the sides closely surrounding the specimen, providing most views. The fly is virtually complete, portions of the left side (head, thorax) are lost or damaged, and some parts have been distorted by compression. The section with the fly was trimmed from a cabochen that also contains several thrips (Thysanoptera). The area around and including tergite 1 is poorly preserved, but judging from the lack of setae in this area (which cover other tergites and a portion of tergite 1), it appears that a substantial portion of tergite 1 is membranous. The abdomen is held slightly raised.

Figures

FIG. 5. Archosolva sulcata, new genus and species (Xylomyidae), JZC Bu-208, holotype. A. Wing. B. Anterior portion of head (lateral view), with detail of antennal tip. C. Female terminalia, dorsal view.

FIG. 6. Lateral views of thoraces of Burmese amber Stratiomyomorpha. A, B. Stratiomyidae. C, D. Xylomyidae. A. Normyia longistyla, new genus and species. B. Narcissomyia bella, new genus and species. View is slightly ventral. C. Archosolva biceps, holotype (note inflated metacoxa). D. Archosolva sulcata, holotype (note fossa, for apparently receiving the raised mesofemur).

FIG. 36. Archosolva sulcata, new genus and species (Xylomyidae), holotype JZC Bu-208. A. Habitus, dorsal view. B. Antennae, dorsal view. C. Left wing. D. Terminalia, dorsal view. E. Head and thorax, right lateral view.