Leucostoma aterrimum ( Villers, 1789 )

Leucostoma aterrimum ( Villers, 1789) View in CoL

Musca aterrima Villers, 1789: 548 View in CoL .

Leucostoma neomexicana Townsend, 1892: 169 View in CoL . Cyclodionaea acuminata Townsend, 1915: 234 View in CoL .

Diagnosis: Females are easily distinguished from other Leucostoma by their long and slender abdomen, tapering distally ( Fig. 6 View Fig ). All abdominal segments are similar in length/width ratio, however, the fourth tergite is telescopically retracted and seems wider (the retracted anterior portion lacks strong setulae). The males resemble L. simplex , according to Reinhard (1956), but the abdomen has pruinosities on the last two segments and is narrowed distally, not as much in females. Other characteristics are used in Reinhard’s identification key. The male terminalia ( Fig. 4 View Fig ) likely has some features that will distinguish them from other Leucostoma species, but we lack material and illustrations to compare.

Redescription: Male ( Fig. 6A–B View Fig ). Body length 4.6–5.5 mm.

Coloration: Head brown to black with strong silver pruinosity; frontal vitta black. Scape and pedicel brown, first flagellomere black, brown basally; arista brown. Palpus pale tawny and prementum brown. Thorax black to brown with weak silver pruinosity dorsally and laterally. Thoracic spiracles brown. Wing hyaline, veins at base pale yellow. Calypters white. Halter pale brown. Legs dark brown to black; claws black; pulvilli pale tawny. Abdomen dark brown to black, tergites 4 to 5 fully covered with silver pruinosity.

Head: Holoptic. Eye bare. Frontal vitta narrow, slightly narrower than fronto-orbital plate maximum width. Ocellar setae hairlike, lateroclinate. Eight to 11 frontal setae, hairlike, descending to pedicel level. Fronto orbital plate and dorsal part of parafacialia covered with setulae. Inner and outer vertical setae not differentiated from surrounding postocular setae. Postocellar setae hair-like. Antenna inserted at middle level of eye, short, not extending to vibrissa level. Lunule setulose. Scape short, about one-quarter length of pedicel. Pedicel setose dorsally, with 1 strong seta. First flagellomere slightly longer than pedicel, elliptical but broader distally. Arista micropubescent. Vibrissa strong, 4–5 subvibrissal setae. Eye about 0.8 to 0.9 head height. Gena about 0.1 eye height. Antennal axis slightly subequal to oral axis. Lower facial margin slightly protruding. Palpus slightly clavate. Prementum short, about half eye height. Labella well-developed, as long as first flagellomere.

Thorax: Prosternum bare. Proepisternum bare. One strong proepimeral seta, surrounded with weaker setae. Anterior spiracle with both lappets well-developed, covering almost entire opening. Posterior spiracle with posterior lappet slightly larger than anterior. Acrostichal setae 1+1, with another presutural long setula. Dorsocentral setae 2+3. Intra-alar setae 1+2. Supra-alar setae 1+3, the first and third postsutural short. Postpronotal lobe with 3 setae, and 2 anterior long setulae. One postalar seta. Scutellum with one basal, one lateral, and one decussate apical pairs of setae. Two katepisternal setae, with posterior seta longer. One anterior and five posterior anepisternal setae. One anepimeron seta. Katatergite and anatergite bare. Wing: subequal to thorax + abdomen length. Ratio of wing length/maximum wing width 2.3–2.6. Costal spine not differentiated. Costal vein without breaks, beyond intersection with Sc vein without ventral setulae. Cell r 4+5 with long petiole, petiole more than three times r-m length, ending before wing apex. Base of vein R 4+5 with 1 dorsal and ventral setae. Crossvein dm-cu slightly curved. Calypters rounded, large, reaching end of syntergite 1+2. Legs: Fore coxa with many anterodorsal setae. Fore femur with row of posterodorsal and posteroventral seta. Fore tibia with one posteroventral seta. Mid coxa with row of setae on anterior surface. Mid femur with rows of anteroventral and posteroventral setae on basal half, two posterodorsal preapical setae. Mid tibia with three anterior, two posterodorsal and two ventral setae. Hind coxa with row of anterodorsal setae. Hind femur with rows of anterodorsal, anteroventral and posteroventral setae on basal half, two anteroventral preapical setae. Hind tibia with three to four anteroventral setae, row of anterodorsal short setae with two strong, three to two posterodorsal setae. Tarsal claws longer than fifth tarsomere.

Abdomen: Elliptical, slightly pointed at apex. Abdomen fully covered with long setulae. Median marginal setae and lateral marginal setae on all tergites, row of marginal setae on tergite 4 and 5. Abdomen 1.5–1.7 times as long as wide, 1.1–1.2 times as long as thorax in dorsal view. Sternites partially covered by tergites. Sternite 5 plate-like, posterior margin slightly invaginated.

Terminalia ( Fig. 7B View Fig ): Tergite 6 partially fused to syntergosternite 7+8. Sternite 6 symmetric, V-shaped, connected by a membrane with tergite 6 and syntergosternite 7+8 on both sides. Epandrium arched, with setae; epandrium anterior process narrow. Bacilliform sclerite thin, elongate. Hypandrium with hypandrial apodeme slightly concave, with rounded apex in ventral view; hypandrial arms not fused dorsally; hypandrial central plate extended posteriorly, ending as two elongated pointed arms. Pregonite small, hard to differentiate, fused with hypandrium and postgonite; with sensory pits. Postgonite short and elongated, pointed apically. Phallapodeme rodlike, slightly enlarged in both ends, subequal to hypandrium length. Phallic guide not distinguished. Ejaculatory apodeme small, rod-shaped. Epiphallus not differentiated. Basiphallus as curved tube, with two anterior dorsal projections, fused with distiphallus. Distiphallus as a flattened ribbon, short. Syncercus fused, elongated, and pointed distally, the tip directed anteriorly in lateral view. Surstylus triangular, short.

Female: Differs from male as follows. Head with only strong silver pruinosity and dichoptic. Ocellar setae stronger. Frontal setae stronger, with 5–7 setae, the posterior lateroclinate. Two proclinate fronto-orbital setae. Inner and outer verticals stronger, the latter directed laterally. Thorax with stronger silver pruinosity; in presutural scutum delimiting two diverging median black stripes and two triangular lateral black spots. Three katepisternal setae. Calypters slightly shorter. Fore tibia with three anterodorsal and one posteroventral. Mid tibia with four anterior setae. Tarsal claws shorter and more curved, pulvilli shorter. Abdomen with silver pruinosity band stronger on tergite 3, weak on tergite 4. Abdomen longer and narrower, tapering gradually from base to apex; abdomen 2.3–2.5 times as long as wide, 1.5–1.7 times as long as thorax in dorsal view. Tergite 5 anterior part telescopically inserted in abdomen.

Terminalia ( Fig. 4B View Fig ): Sternite 5 plate-like. Tergite 6 strongly modified as two pincer structures; each posterior projection elongated, with setae modified as spines; not fused dorsally; not fused to sternite 6. Sternite 6 subquadrate, posteriorly deeply invaginated. Tergite 7 divided in two separated pieces, with anterior elongation, and with a setulose lobe posteriorly. Sternite 7 as an elongated plate, with two anterior projections; posteriorly deeply invaginated medially, forming two lobes with setulae. Segment 8 fused; with a narrow-fused arch dorsally (probably part of tergite 8); ventral part elongated anteriorly, with a posterior bent piercer, projecting dorsally, then curving downwards (sternite 8). Epiproct and hypoproct not recognizable. Cerci elongate and thin, setulose posteriorly. Three spherical spermathecae.

Puparium ( Fig. 5B View Fig ): Elliptical, without horns or conspicuous spines. Posterior spiracle at the end of conical tubercle, with two sinuous spiracle openings.

D i s t r i b u t i o n: Nearctic: Canada, U.S.A. Neotropical: Argentina, Brazil (new record), Chile, Mexico, Peru (new record), Puerto Rico, Palearctic: “Europe” (type locality of M u s c a a t e r r i m a). Australasian & Oceanian: Hawaii (immigrant) ( O’Hara et al. 2020).

Examined material: BRASIL: 1ñ (CEIOC), Rio de Janeiro, Jardim Botânico, vi.1936, H.S. Lopes; 1ñ (CEIOC), São Paulo, Cantareira, Horto Florestal, iii.1936, S. Lopes, col.; 1ò (MZSP), São Paulo, Bebedouro, Andes, ii.1955, M Carrera col. PERU: 4ò, 5ñ (MZSP), Arequipa, Santa Rita, 10.vii.2015, G. Mamani col.

Host list

Hemiptera (Heteroptera) , Rhopalidae Liorhyssus hyalinus (Fabr.) ( Arnaud, 1978)