Bittacomorphinae, Alexander, 1920

Fasbender, Andrew & Courtney, Gregory W., 2017, A revision of Bittacomorphinae with a review of the monophyly of extant subfamilies of Ptychopteridae (Diptera), Zootaxa 4309 (1), pp. 1-69 : 26-27

Subfamily Bittacomorphinae Alexander (1919)

Bittacomorphinae Alexander, 1919: 779 , 790 (first usage) Bittacomorphinae Alexander, 1920: 779 (diagnosis)

Bittacomorphinae Alexander, Alexander 1927: 7 (catalog)

Diagnosis. Larva. Head capsule broadly trapezoidal to rounded, with genae variable in shape; two antennal segments; postmentum fused with postgena, at most two lobes on anterior margin. Antenna with one article. Integument with tubercles. Prolegs well developed; abdomen without creeping welts. Pupa. leg sheaths with tarsi of forelegs overlapping tarsi of hind legs. Adult. 10–35mm long, delicate fly with dark coloration and white bands on legs. Antennae with>18 flagellomeres. Scutum without complete transverse suture. Wing with M unbranched.

Tibial spur of foreleg modified to furcate, fleshy lobe. Male genitalia with aedeagus directed posteriorly. Female genitalia with exposed, platelike epigynium; flexible tab-like cerci.

Description. Larva. Head capsule weakly to strongly deflexed, shape variable; antennae with two segments; postgena fused to postmentum, anterior margin variable, never serrate. Cuticle translucent, typically with adhered iron oxide giving an orange or brown appearance; integument covered in prominent tubercles forming ordered rows. Prolegs strongly developed, distinctly cylindrical protrusions on ventral surface of abdominal segments I–III, with scythe to sickle shaped claw. Abdominal segments I–V lacking creeping welts. Adult. Head strongly appresed to thorax, triangular to subovoid; frons wider than long, convex medial suture variable, sparsely provided with setae; genae with sparse setae if present. Scape subovoid, 18–20 flagellomeres, proximal flagellomeres elongate, shortening distally, distal flagellomere reduced to button-like structure; verticillate trichoid sensilla not present. Face indistinct from clypeus which incises it. Clypeus acutely triangular, labrum small, spear to peg shaped. Maxillary palpus ultimate segment never greater than 1.25x length of preceding segment. Labium often extending beyond sclerotized portion of clypeus, variably shaped labella fused or unfused medially. Cervical area not visible in undissected individuals. Antepronotum thin plate behind head, widening slightly above forecoxa where it is provided with sparse setae, not teardrop shaped. Prescutum anterior margin straight. Prescutal suture often indistinct, incomplete; sagittal suture distinct anteriorly, fading at terminus of prescutum. Prescutum terminating approximately 7/8ths length of scutal complex or near the scutellum. Prescutellum present or absent. Scutellum ovoid, with postalar ridge rounded anteriorly. Postalar wall slightly folded anteriorly. Mediotergite sagittal suture present, weakened posteriorly. Paratergite variable. Episternum glabrous, flat; anepisternal suture faint, complete or incomplete. Epimeron with subtriangular posterior margin. Laterotergite ovoid, slightly domed, upper portion freckled with sparse setae, without prominence over halter. Metapleuron rectangular, taller than wide, tapering ventrally; metapleural suture variably developed. All pleural sclerites without setae, heavily pollinose. Wing less than ½ body length, hyaline, macrotrichia present or absent on membrane and veins; C ending at apex of wing, R3+R4+5 fork contiguous with rm, M simple, CuA2 sigmoidal. anal lobe reduced. Legs dark, banded with white; femur strongly narrowing towards trochanter; tibial spur on foreleg heavily modified, fleshy, bifurcated to two unequal lobes, convergent apically; 1 st tarsomere variable. Abdomen narrow in both sexes, without telescoping of sclerites until after 5th segment. Male. Epandrium bilobate or platelike, posterior margin variable; epiproct indistinct, hypoproct ovoid or tonguelike; two prominent articulated epandrial claspers directed posteriorly or posteroventrally. Parameres separate, stylate, with web-like membrane medially. Gonostylus simple tapering lobe (with basal lobe in Bl. fenderiana ), apex rounded or flattened on medial margin. Gonocoxite without secondary lobes. Hypandrium in horizontal plane, divided into basal and terminal divisions by distinct joint. Terminal division significantly smaller than basal division, pouchlike or foliform. Sperm sac well developed, filling most of segment VII of abdomen, subspherical—narrowing slightly at juncture with aedeagal sclerites; two membranous windows formed at junction with ventral lobes of lateral ejaculatory process, which protrude into the sac; ejaculatory apodeme much smaller than sperm sac, on posterior surface dorsal to aedeagal sclerites, tapering; lateral ejaculatory processes wing-like, directed laterally, ventral lobe prominent. Aedeagal sclerites longer than 2x width, apical apodemes prominent and articulating with subaedeagal sclerite; subaedeagal sclerite with ventral arms articulating with hypandrium. Female. Epigynium exposed, platelike, generally pentagonal in shape; epiproct absent to distinct, hypoproct tonguelike; cerci tablike, subquadrate to rounded, setose, lightly sclerotized and flexible. Hypogynium with hypogynial valves, medial emargination variously developed, lateral apices often extended to lobes. Spermathecae absent or unsclerotized.

Taxonomic notes. The first flagellomere is often subdivided in Bittacomorphinae , resulting in differing antennal flagellomere counts between individuals of the same species.