Bolbomyia Loew

Kerr, Peter H., 2010, 2592, Zootaxa 2592, pp. 1-133 : 71-73

Genus Bolbomyia Loew

Figs. 4, 27, 43, 68, 89, 114, 136, 168.

Bolbomyia Loew 1850: 39 . Type species Bolbomyia nana Loew 1862: 188 , by subsequent monotypy.

Misgomyia Coquillett 1908: 145 . Type-species Misgomyia obscura Coquillett 1908 , by original designation. Cekendia Szilády 1934a: 264 (as subgenus of Ptiolina Zetterstedt 1842 ). Type species Ptiolina (Cekendia) wuorentausi Szilády 1934 , by monotypy.

Cechenia Frey 1954: 9. Unjustified emendation.

Diagnosis. The best autapomorphy defining Bolbomyia species is the female terminalia, which have only two spermathecae and whose ducts lead directly to the genital chamber and attach to this structure independently, without joining into a common duct. Each of the spermathecal ducts has a noticeable bulbous swelling along its length. Aedeagal tines are present in the male genitalia of Bolbomyia . Although aedeagal tines are also found in Arthroceras and in members of Athericidae and Tabanidae , the tines in Bolbomyia are likely independently derived and may represent another autapomorphic character state.

Species of Bolbomyia are small (2.3 to 3.5 mm), brown or black in color, with lightly infuscate wings, restricted to the north temperate region of North America and eastern Asia (Kamchatka). Males holoptic; antenna with basal flagellomere enlarged, elongate oval or subconical, laterally compressed, bearing 2 to 3 distal flagellomeres; laterotergite bare; M 3 absent; tibial spur formula 1:2:2; and tibia without macrochaetae. The fore tibial spur will separate Bolbomyia from nearly all other small brachycerans. Litoleptis is similar in size and appearance, but lacks tibial spurs on all tibiae, bears a single elongate antennal flagellomere, and lacks the discal medial cell of the wing. Ptiolina is larger and more robust, and may be distinguished from Bolbomyia by the presence of M 3, by having only one hind tibial spur, and antenna with enlarged first flagellomere with a single-segmented style.

Description. Head. Clypeus not bulbous. Scape approximately same size as pedicel. Flagellomeres 3 to 4; first flagellomere enlarged, elongate oval or subconical, laterally compressed, bearing weak setae; distal flagellomeres cylindrical, short (except terminal flagellomere which is more elongated). Eyes inconspicuously setulose; in female, dichoptic; in male, holoptic, not flattened dorsally, ommatidia split into dorsal and ventral areas and smaller ventrally. Labella lacking pseudotracheae, shorter than palpus. Theca short and stout; lateral sclerites adjacent and touching, but mostly separated. Palpus two-segmented; distal segment longer than or subequal in length as proximal segment. Stipes surrounded by membrane above theca, directed posteriorly. Cardo not swollen. Lacinia shorter than palpus, tip not serrated. Mandibles absent. Cibarial pump short, as wide as long or wider. Cornu nearly as long as or longer than cibarial pump. Pharyngeal pump narrow along most of length, mostly flat, longer than length of cibarial pump (cibarial pump very short).

Thorax. Mesonotum without vittae. Dorsocentral setae not longer than other mesonotal setae. Anepisternum bare or bearing 1–2 setulae. Laterotergite bare. Postspiracular scale absent. Proscutellum present or absent. Subscutellum not enlarged nor lengthened; inconspicuous. Wing membrane lightly infuscate, without markings, pterostigma absent or lightly present. Lower calypter reduced. Upper calypter well developed with broad curvature, lobe-like, width twice length or less. Costa extends past wing tip, to approximately R 5. Humeral crossvein well developed. Sc-r crossvein absent or weakly developed, positioned distal to h by less than length of h. Dorsal side of R 1 setulose, ventral side bare. Dorsal side of R 2+3 with or without setulae, as ventral side. All other wing cells and veins bare. R 2+3 sinuous, apical third of R 2+3 ultimately bends slightly toward wing tip; longer than R 5, but less than twice as long. Base of R 4 –R 5 fork distal of distal end of cell dm. R 4 at base relaxed, not strongly curved; nearly straight apically. R 5 anterior to, posterior to, or ending at wing tip; clearly longer than R 4+5 (r-m to R 4 origin). M 3 wing vein absent. M-cu crossvein absent. Origin of CuA 1 at discal cell. CuA 2 greater than 2/3 length of posterior vein of cell bm. Alula with narrow or broad curvature, rounded evenly. Anal lobe well developed. Cell cu p open. Halter knob 2/3 or longer than length of stem. Tibial spur formula 1:2:2. Hind coxal tubercle present. Hind tibial macrochaetae absent. Postmetacoxal bridge present as incomplete, thin extension.

Abdomen. Terminal abdominal segments 5–10 evenly tapered from segments 1–4. In female, tergite 7 much longer than wide. Intersegmental membrane between segments 7 and 8 short, as throughout abdomen. Sternite 8 cleavage superficial, open broadly; longer than wide or as long as wide. Male terminalia with epandrium simple, not containing hypandrium ventrally. Epandrium wider than long, modestly curved anteriorly. Tergite 10 absent. Hypoproct triangular (rounded posteriorly); rounded, virtually encircling cerci; not fused with cercus; anterior and posterior margins entire, evenly sclerotized; tomentose, without setae. Cercus displaced away from epandrium; partially displaced from one another, separation distance approximately half width of single cercus; held horizontal in relation to rest of abdomen; in posterior view cupped, forming circular outline medially. Hypandrium separated from gonocoxites by complete suture. Gonocoxite with sinuous dorsal ridge, leading to gonocoxal apodeme. Gonocoxal apodemes short or long enough to reach anterior margin of hypandrium. Sperm sac not developed into bulbous sac or separate lobes. Lateral ejaculatory processes absent. Ejaculatory apodeme moderately long to long, reaching anterior margin of hypandrium, or somewhat beyond this. Ejaculatory apodeme tripartite; dorsally compressed laterally and ventrally, compressed dorso-ventrally. Aedeagal tines present. Endoaedeagal process present. Female terminalia with two spermathecae; spherical or elongate oval; sclerotization light to none. Spermathecal ducts less than three times length of sternite 9. Spermathecal duct accessory glands absent, but ducts with large swelling at approximately mid-point along their length. Circular ridge present at distal end of reinforced base of spermathecal ducts. Ejection apparatus of spermathecal ducts thickened, sclerotized, with ringed surface furrows; swelling present halfway between genital chamber and spermathecae. Common spermathecal duct absent. Genital chamber oval, moderately sized. Accessory gland posterior to genital chamber inconspicuous, easily overlooked even after staining. Sternite 9 anterior end narrow with rounded tip; posterior end with narrow lateral extensions, free, held in vertical plane. Tergite 10 short (length less than half width). Sternite 10 roughly pentagonal, pointed posteriorly; posterior half below first cercal segment. Cercus two-segmented. First segment of cercus not elongate, with ventral process. Ventral lobes of first segment of cercus not curving ventrally towards one another to form ring (sometimes slightly arched medially, but forming narrow elliptical opening only). Basal cercal segment adjacent dorsally. Second cercal segment not elongated, with apical sensory pits.

Larva. Unknown.

Biology. Chillcott (1963) reports that females of Bolbomyia are frequently collected from flowers, whereas the males are usually at rest on nearby vegetation. D. Webb (pers. comm.) collected Bolbomyia nana in a small forest clearing with a fern understory in North Carolina ( USA). Jeff Cumming, Richard Vockeroth, and others including myself, have had success sweeping Bolbomyia nana from low-lying vegetation in small forest clearings in and around the hill-top of King Mountain, Gatineau National Park, in Quebec ( Canada). Details of its life history are not known. The flight period appears to be exceptionally short, lasting only a couple weeks or perhaps as little as a few days per year (depending on weather conditions).

Members of the genus inhabit the Russian Far East, Canada, and the USA. One species is known from Baltic amber.

Literature. Webb (1987a) provides a key for the extant species of the world.