Lasiopogon rokuroi Hradský

(Figs. 15, 16)

Lasiopogon rokuroi, Hradský, 1981: 180 .

Small to medium black flies, 9–12 mm. Recognized by the gray thorax, black abdomen and dark wings.

Adult. Male.

Head: Face light gold/gray tomentose; vertex black with gold/gray pollen and long black curved hair; occiput gray pollinose with black curved hair. Mystax hair black. Genal hair long, fine white merging into black proclinate postocular bristles. Antenna black, dusted with gold pollen on edges and apices; black bristles. Relative lengths of segments: 3>1>F2+3>2. Thorax: Scutum brown, tinged gray. All bristles black. Thin dark brown median stripe of scutum disappearing medially; broader dark brown paramedian stripes. Long sparse black acrostical hair; sparse long dorsocentrals. Chaetotaxy with: 2 posthumeral, 3 presutural, 2 supraalar, and 3 postalar bristles. Scutellum gold/gray pollinose ringed with 1 row of dense black bristles. Pleura gray pollinose with black bristles and sparse fine white hair. A short row of black katatergal bristles. Posterior margin of anepimeron with long sparse, black hair. Legs: Black with black bristles and hair; fine long white hair. Posterior coxal peg absent. Femora with long dense fringes of fine white hair. All tibia with black bristles. Wings: Tinged black. Radial medial crossvein (r-m) positioned basal above discal cell (Fig. 2). Halter knob yellow, without spot. Abdomen: Male. Black/brown with white hair and black tomentum; tergite apices with light gray pollen bands. Tergite 1 with 2 strong black latero-apical bristles, tergite almost completely covered in gray pollen. Gray pollen extending to tergite bases laterally. Male genitalia (Figs 15 & 16). Epandria shiny black with gold/gray pollen. Gonostylus apex excised, narrowed to a fine point.

Female. Similar to male except light gray tergal bands broader. Base black color of abdomen may appear as a dark brown.

Material examined. Kangwon Province. 5ɗ, 4Ψ (1 pair in cop.): 5/V/2003, Odaesan N. P., North Side 500 m., 37°48’49”N, 128°42’29”E.

Kyongsangnam Province. 8ɗ, 15Ψ (1pair in cop.): 27/IV/2002, Chiri Mt., Taewonsa Temple. 10ɗ, 1Ψ (1 pair in cop.): 18/V/2003, Samjeong–Ri, Mach’on, 35°20’55”N, 127°38’21”E. 7ɗ, 6Ψ: Same data except: 27/ VI/2003.

Field notes. Lasiopogon rokuroi inhabits wooded uplands along slow moving, narrow rivers and streams. The asilids settle mid stream on boulders and fallen logs where they prey on emerging caddisflies (Trichoptera). They are sympatric with L. akaaishii and have a similar flight period. They mate in a tail-to-tail position. See Table 1 for prey and seasonality.