Archosolva biceps, 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 : 14-16

Archosolva biceps , new species

Figures 4 , 6C , 35

DIAGNOSIS: Distinguished from Archosolva sulcata , n. sp., by the following: head broad frontally; metacoxa bulbous, inflated; metafemur stout; cell m relatively small, narrow; CuA 1 base connected directly to base of M 3, forming short stem as part of cell d (i.e., no crossvein m-cu).

DESCRIPTION: Based on unique female. Body length 4.80 mm; head width 1.14 mm; thorax length 1.74 mm; wing length 3.34 mm; abdomen length 2.61 mm (including cerci). Head: Short, compressed anteroposteriad, with broad anterior and posterior surfaces. Frons bare, dark, smooth. Ocelli on slightly raised mound, anterior ocellus facing forward, slightly farther from posterior ocelli than posterior ocelli are to each other. Face slightly concave, clypeus slightly raised. Occiput slightly concave. Eye: Large, occupying all of lateral surface of head in lateral view, with broad frontal surface; completely bare, facets not differentiated; inner (mesal) margins widely separated, slightly divergent anteriad, width slightly greater than distance between outer margins of ocelli. Antenna: Submoniliform, stout at base, evenly tapered to narrow apex, with 8 flagellomeres and minute apical style. Scape, pedicel small, slightly cone shaped; flagellomere 1 largest (broadest and longest flagellomere), flagellomeres 2–5 compact, short; flagellomere 8 slender, length approximately equal to flagellomere 1; sensillar foveae visible on basal flagellomeres. Mouthparts: Well developed; palps porrect, apex reaching nearly to antennal bases, basal palpomere slender, apical one laterally broad, roughly triangular, slightly longer than basal palpomere. Labellum well developed (lobes parted in type), broad, flat, subovoid, with ca. 12 pseudotracheae. Thorax: Scutum moderately arched, scutellum flat, both with very fine, dense, setigerous punctation; patch of fine, stiff setulae on portion of laterotergite just anterior to posterior spiracle; sparse punctation on anepisternum and katepisternum. Transverse suture deeply and discretely impressed laterally; suture shallow, short, ill defined dorsolaterally. Postpronotal lobe long and narrow in dorsal view; postpronotum well developed, immediately ventral to lobe. Scutellum broader than long, margin evenly curved in dorsal view, no spines; small proscutellum and small subscutellum present. Pleura overall oblique, ventralmost portion of katepisternum significantly posterior to level of anepisternal cleft. Wing: Of moderate length and width, W/L 0.5. All veins sclerotized, except for base of Sc (which is spectral); fine setulae only on stem of R and R 1, base of R 4 -R 5 stem. C ends just past tip of R 5. Sc long, complete, 0.54× length of wing. R 1 very close and parallel to Sc; Rs short, without thickened node or weak area; R 2+3 short and par- allel to R 1; no pterostigma; fork of R 4 -R 5 slightly asymmetrical, R 4 0.75× length of R 5; tip of R 5 meeting wing apex. Crossvein r-m near base of cell d; cell d slender, W/L 0.3; vein M 3 short, meeting CuA 1 well before wing margin; cell m an isosceles triangle, W/L 0.38. CuA 1 base con- nected directly to base of M 3, forming short stem as part of cell d, lacking crossvein m-cu. Cells br, bm of equal length; cell cup closed, CuP distinct; tips of M and Cu veins distinctly tapered but meeting wing margin. A 2 well developed; anal lobe, alula, upper calypter present but narrow. Legs: Relatively short, robust. Pro- and mesocoxae slender, distant from each other; metacoxa swollen and inflated laterally. Metafemur significantly thicker than other two femora, without ventral spines or tubercles. Lengths of leg segments: femur> tibia> basitarsus> combined lengths basitarsomeres 2–5. Tibial spurs 0-?-2 (apices of mesotibiae lost/obscured). Pretarsus with claws well developed, simple; pulvilli slen- der, shorter than claws, empodium pulvilliform, smaller than pulvilli. Abdomen: Very broad basally, broader than thorax, evenly tapered to narrow apex; held slightly elevated. Dorsum of abdomen relatively flat; length of tergite 2 approximately equal to t3; tergite 2 fully sclerotized; tergite 1 with central depression beneath scutellum (probably membranous area). Tergites 1–5 each with deeply impressed transverse sulcus near middle of each tergite. Original color of abdomen apparently dark; tergites with dense, very fine, setigerous punctation. Tergite 9 very small, barely exposed; tergite 10 very small, transverse, not separating basal cercomeres. Cercus long, slender, length ca. equal to tergite 8 length; basal cercomere slightly longer, both segments with fine, sparse setae. Sternites 3–7 well developed (1, 2 obscured); apical margin s7 with small pair of lobes.

TYPES: Holotype, female, JZC Bu-257.

ETYMOLOGY: From the Latin biceps (“twoheaded” or “double-peaked”), in reference to the swollen metacoxa and metafemur.

COMMENTS: Specimen is complete and very well preserved, only a few important features are obscured (e.g., mesotibial spurs). The fly is preserved in a piece of deep yellow amber of irregular shape, 5 × 7 × 10 mm, all surfaces flattened for most views of the fly. The piece was trimmed from a cabochen that also contains stellate trichomes, a psychodid midge, serphitid wasp, and parts of a spider. The stout metafemur and coxa suggests a relationship to Solva (but without ventral tubercles), and the abdomen is held slightly raised.

Figures

FIG. 4. Archosolva biceps, new genus and species (Xylomyidae), JZC Bu-257, holotype. A. Wing. B. Detail of antenna. C. Head, ventrolateral view. D. Mesotibial apex with spurs. E. Female terminalia, left ventrolateral view. Panels B, D, E to same scale.

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. 35. Archosolva biceps, new genus and species (Xylomyidae), holotype JZC Bu-257. A. Dorsofrontal view of habitus. B. Habitus, right lateral view. C. Head and thorax, oblique dorsal view.