Syringogaster miocenecus Grimaldi, 2009

Marshall, S. A., Buck, M., Skevington, J. H. & Grimaldi, D., 2009, A revision of the family Syringogastridae (Diptera: Diopsoidea), Zootaxa 1996 (1), pp. 1-80 : 71-72

Syringogaster miocenecus Grimaldi , new species

Figs. 63–67, 74, 75; Plate 7A

DIAGNOSIS: Distinguished from S. craigi , also in Dominican amber, by slight differences in the wing shape and venation ( S. miocenecus wing shorter and relatively wider: wing length/width 3.3, vs. 4.10 for S. craigi ; apex of R 2+3 ending at level of crossvein dm-cu, vs. distal to it in S. craigi ), by the head shape (frontally rounded and with tall face in S. miocenecus ; vs. with long, flat frons and very short face in S. craigi ); by the bare ventral surface of fore basitarsus (vs. with long, fine setulae [possibly sexually dimorphic]) and bare lateral surface of hind femur (vs. with two rows fine setae); and the more conical base of the abdomen at syntergite 1–3 (vs. thinner, more cylindrical). DESCRIPTION: Based on holotype female. General coloration: Head and thorax (including petiolate segment) dark brown to blackish brown; abdomen with anterior segments light, grading into darker brown apicad. Legs light brown, graded on basitarsus to light tan/ yellow. Tarsi 2–5 pale.

Head shape approximately hemispherical, posterior (postoccipital) surface flatter; occipital foramen produced into short supracervical collar approximately same length as pronotum. Ocellar triangle well defined, shiny, large; lateral margins virtually converge on dorsal portion of ptilinal fissure. One pair of ocellar and outer vertical setae present; each thick and black; ocellars slightly shorter than outer verticals. Eyes large, deep, occupying entire lateral surface of head; no subgenal space below eyes, nor visible genal setae/setulae. Face light; high and narrow, height slightly greater than half the head height; face width approximately one-half the width between anterior margins of eyes; ptilinal fissures slightly convergent ventrad. Ocelli and ocellar setae on small, dark ocellar mound; bases of setae very close (separated by diameter approximately equal to diameter of setal base). Apical (flagellate) portion of arista slightly longer than twice the length of flagellomere 1, short plumose/bipectinate, with seven dorsal and five ventral branches (as figured; extant species usually have 8–12 dorsal branches and 1–2 fewer ventral rays).

Thorax dark brown to black; length (base of supracervical collar to tip of scutellum) 1.02 mm. Pronotum large, projected anteriad, forming collar with occipital foramen. Humeral carina well developed, extended from humeral lobe to transverse suture. Transverse suture well developed, extending to approximately onehalf the width of mesoscutum. Scutellum small, evenly rounded; postnotum large, bulging, projecting slightly beyond apex of scutellum. Pleura deep, dark, shiny, devoid of macrosetae; many sutures fused; proepisterna with ventral median keel-like carina running from fore coxae to midway between fore and mid coxae. Fore femur and tibia without spines. Mid femur with smooth, thin strip of cuticle ventrally on distal third (glandular area?). Sawlines present on mid and hind tarsomeres 1–3. Mid coxae with bases fused to thorax, otherwise largely membranous. Hind legs with bases contiguous medially; coxae free but small and mostly membranous, smaller than trochanter. Hind femur incrassate, swollen, with dark coloration on anterodorsal surface near proximal end. Two longitudinal rows of thick, stout, sclerotized spines ventrally: nine spines in anterior row, five in posterior row. Hind tibia curved to fit against spinose surface of femur, with one row of spines on each side of adpressed tibia. Anterior half of hind tibia with narrow trough on ventral surface. Lengths of femora: fore 0.54 mm, mid 0.83, hind 0.99.

Wing length (tip to base) 2.45 mm; slender, length/greatest width = 3.3. Largely hyaline, with infuscate areas: 1. near apex of R 2+3 (darkest area on wing) to around crossvein dm-cu (but much more diffuse here); 2. around crossvein r-m; and 3. a slight band encompassing basal fork of Rs, crossvein m-cu, and CuA 2. Veins and crossveins distinctly darkened in infuscate areas. Spinule-like setae absent on segment of costal vein proximal to apex of R 1; vein C ends slightly posterior to wing tip, connected to tip of M. Sc present as distinct vein, incomplete and tapered apicad, runs very close to R 1. Base of wing bare of microtrichia (as figured), microtrichia much more dense over crossveins and infuscate areas. Microtrichia irregular but in rows near margins of wing and on anal lobe. Vein proportions as figured; longitudinal veins slightly sinuous. Apices of veins CuA 1 and A 1 +CuA 2 abruptly ended approximately midway between vein base and wing margin. Wing margin with dense fringe of fine setulae; setulae sparse on anal lobe and alula. Halter light, in contrast to dark brownish-black of thoracic ‘petiole’ on which they are based.

Abdomen: Approximate length (tip to base of petiole) 1.85 mm. Abdomen yellow apically, dark brown at apex and graded to light apicad; surfaces largely bare, with scattered setae at posterior end. Very weak suture possibly present between tergites 1 and 2 (any suture between tergites 2 and 3 obscured by the wings that overlap the abdomen). Syntergite 1–3 approximately two-thirds the abdomen length, not parallel-sided, but conical shaped. Spiracles difficult to observe, but clearly reside in membrane on segment 5 near tergal margin, and within tergite 6. Spermathecae unknown. Hypoproct simple, setulose; cerci setulose, approximately onehalf the size of hypoproct.

TYPE MATERIAL: Holotype ♀: AMNH DR10-1427 , a complete specimen beautifully preserved in a clear yellow piece of Miocene amber from the Dominican Republic. Exact provenance within the Dominican Republic is unknown. The amber piece measures 8 x 8 x 3 mm and is polished flat on opposite sides of the two broadest surfaces, to maximize dorsal and ventral views of the fly. There is a slight orange halo around the fly and the piece contains no other inclusions except some scattered lepidopteran scales. Deposited in the AMNH amber fossil collection, Division of Invertebrate Zoology.

ETYMOLOGY: Referring to the Miocene age of the amber.

COMMENTS: The coloration and body proportions are very similar to those of S. craigi , also in Dominican amber but known only from a male specimen. At first it was considered that the two specimens may be male and female of the same species, but the significantly different wing proportions and more subtle differences in venation and coloration suggest otherwise, as do the disparate shapes of the heads. These differences correspond with variation in the setation of the legs, discussed in the diagnosis, though the setose fore femur in S. craigi could be a sexually dimorphic character, since various male acalyptrate flies have frequently evolved brushes on the forelegs. Lastly, though significant intraspecific variation in size occurs in schizophorans, the significantly larger male (by c. 10%) is opposite the sex differences typically found in Schizophora (including recent syringogastrids). Relationships to, and differences from, extant species are discussed above under the heading “Characterization of species groups”.