Leptoconops (Leptoconops) torrens (Townsend)

Phillips, Robert A., 2022, Culicoides Latreille and Leptoconops Skuse biting midges of the southwestern United States with emphasis on the Canyonlands of southeastern Utah (Diptera: Ceratopogonidae), Insecta Mundi 2022 (907), pp. 1-214 : 28-29

Leptoconops (Leptoconops) torrens (Townsend)

( Fig. 5, 6 )

Tersesthes torrens Townsend, 1893: 371 (female; fig. female head, wing, abdomen, legs; New Mexico).

Leptoconops torrens: Kieffer 1908: 577 (combination; key; male, female; fig. female palpus, antenna male antenna, claw, gonocoxite). Carter 1921: 15 (key; female, male; fig. male gonostylus, claw, antenna, female palpus, antenna, wing stigma). Wirth 1952a: 110 (in part; key; female; male genitalia; fig. female wing, abdomen, palpus, male genitalia). Fox 1955: 263 (in part; key; taxonomy). Whitsel and Schoeppner 1970 (in part; biology).

Leptoconops (Leptoconops) torrens: Wirth and Atchley 1973: 30 (key; female, male; fig. female antenna, palpus, tarsomere 5, spermathecae, head, genitalia, male antenna, genitalia; biology). Atchley 1974: 467 (female; distinction from L. carteri Hoffman ). Downes and Wirth 1981: 397 (fig. male genitalia). Borkent and Spinelli 2000: 9 (in Neotropical catalog).

Diagnosis. ( Table 13) Dark brown to black, tarsomeres often paler; stigma brown; eyes bare; clypeus with eight or more setae; palpal segment 3 sensilla in superficial excavation wider than deep (female as in Fig. 12 L . carteri); hind tibial comb with four spines; claw with basal bristle, without basal tooth. Female: antenna with 12 flagellomeres; mandible with 16–18 prominent teeth; hind tarsomeres 3 and 5 subequal; two elongate spermathecae usually ~1.8× longer than wide (as in Fig. 17 L . carteri), third absent; cerci>3× longer than wide. Male: flagellomere 13 ~1.6× longer than 12; tergite 9 evenly tapering to base of thin widely separated apicolateral processes, which are ~8× longer than wide and separated by a distance about equal to their length; aedeagal sclerites apically fused, blunt; distal sclerite of paramere ~2× longer than wide, apical portion flat, not bent. (Male genitalia nearly indistinguishable from that of L. carteri Fig. 19 .)

Distribution. California, Nevada, Utah (Grand, Kane, Washington counties), and Colorado, south through Arizona, New Mexico and Texas to Baja California and Sonora. A report of L. torrens at Salt Lake, Utah ( Pratt 1907) was a misidentification of L. americanus ( Carter 1921) .

Larval ecology and life cycle. Immatures have been collected from coarse, damp sand and moss in areas protected from floods in washes of mountain canyons (Brenner and Wargo 1984). Also, they and Mullens and Dada (1992b) noted outbreaks occurred several days after major rainfall and lasted 1–3 weeks. Unlike L. carteri , L. torrens males form mating swarms ( Atchley 1973). In the laboratory at 24 °C, Whitsel and Schoeppner (1970) found females laid an average of 42 eggs, of which 42% were viable.

Adult behavior. Known hosts are horse ( Townsend 1893; Wirth and Atchley 1973), human ( Wirth 1952a; Wirth and Atchley 1973), and sheep ( Jones 1965). In contrast with L. carteri , L. torrens tend to bite humans around the head and arms more than on the lower body ( Wirth and Atchley 1973).

In the present study, 53 of the 56 females collected in Utah were while biting humans: two on my ears 8 May 2017, nine on 8 June 1999, and one on 4 June 2001 in Grand County, one by T. Graham on 4 June 2001 in Kane County , and forty on 2–6 June 2019 in Washington County. Two of the other three were CO 2 -trapped in Grand County , and one was collected with UVLT in Washington County where diurnal biting pressure was high—suggesting its capture with UVLT was accidental. Low dispersal from larval habitats may explain why it was rarely CO 2 -trapped ; and strictly diurnal activity would explain its near absence from light traps.

Vector potential. Low parity rates, low dispersal, and short life span were reported for L. torrens , suggesting it has low vector potential (Brenner and Wargo 1984).

Remarks. The Kane and Grand County specimens have uniformly dark brown legs as described by Wirth and Atchley (1973) for California specimens; but the Washington County specimens all have at least their mid and hind tarsomeres paler yellowish brown as they described for other states. Because the females of the low-desert inhabiting L. mohavensis are unknown, it is uncertain if all the L. torrens females collected in Washington County are actually L. torrens . See also L. carteri remarks.

Subgenus Proleptoconops Clastrier

Figures

Figures 3–8. Female wings with cells (lower case) and veins (upper case) labeled. 3) Culicoides stonei. 4) C. atchleyi (Bonneville County, ID). 5) Leptoconops torrens. Female abdomen, ventral view. 6) L. torrens. 7) C. stonei. 8) L. californiensis, dorsal habitus (in alcohol, Yuma County, AZ [Carl Olson, with permission]).

Figures 9–15. 9) Leptoconops americanus female clypeus, setae (s). 10) L. knowltoni female clypeus. 11) L. knowltoni female palpal segment 3. 12) L. carteri female palpal segment 3 (Yolo County, CA). 13) L. werneri female tarsomeres 4–5 and claw (paratype, Imperial County, CA [UCRC]). 14) L. werneri male genitalia, ventral view, tergite 9 apicolateral processes (T9alp), meso-posterior lobe setae (s) (Riverside County, CA [UCRC]). 15) L. belkini male genitalia, ventral view, tergite 9 sclerotized lobe (L) (Riverside County, CA [UCRC]).

Figures 16–19. Leptoconops carteri (Yolo County, CA). 16) Female terminalia with normal spermathecae. 17) Variant with spermathecae similar to those more typical of L. torrens. 18) Lateral view of lower portion of eye showing interommatidial pubescence.19) Male genitalia, ventral view, proximal sclerites and distal shieldlike fusion of the aedeagus (A), proximal and distal sclerites of a paramere (P), tergite 9 apicolateral processes (T9alp).