Culicoides (Silvicola) tristriatulus Hoffman

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 : 96

Culicoides (Silvicola) tristriatulus Hoffman

Culicoides cockerellii, var. tristriatulus Hoffman, 1925: 294 (key; female; fig. wing, mesonotum; California).

Culicoides tristriatulus Hoffman : Williams 1951a: 431 (egg, larva, pupa; 18 fig.). Wirth 1951: 78 (key; female, male; fig. wing, eye separation, palpus, spermathecae, mesonotum, male genitalia). Wirth 1952a: 173 (key; female, male; fig. dorsal thoracic pattern, eye separation, female palpus, male genitalia).

Culicoides (Culicoides) tristriatulus: Khalaf 1954: 39 (assignment to subgenus Culicoides ). Fox 1955: 257 (key and diagnoses of subgenera; species key; taxonomy). Wirth and Blanton 1969b: 238 (key; numerical characters; female, male; fig. female antenna, palpus, wing, spermathecae, eye separation, male genitalia, parameres). Wirth et al. 1985: 12 (numerical characters; fig. female wing). Murphree and Mullen 1991: 314 (key; larva; numerical characters; fig. labium, epipharynx, mandible, hypostoma).

Culicoides (Silvicola) tristriatulus: Mirzaeva and Isaev 1990: 156 in English translation (as part of Cockerellii group, assignment to new subgenus Silvicola ).

Culicoides sordidellus (Zetterstedt) , misidentified: Jenkins 1948: 154 (Alaska).

Diagnosis. ( Tables 14, 15) Wing pattern extensive, with distal stripes and pale spots (as in Fig. 119 , 178 C. cockerellii ); pale spot over at least distal half of r 2; cua 1 without central dark spot; female eyes separated 1–2 ommatidium diameters; superior transverse suture present; palpal segment 3 with scattered sensilla instead of pit; legs without pale bands; fore and hind tarsomeres with apical spines; spermathecae subequal; male tergite 9 apicolateral processes tiny and not projecting beyond median lobe; ventral apodeme of gonocoxite shorter than dorsal apodeme, strongly tapered, pointed, 2× as long as basal width; gonocoxite with fine setae on mesal surface; aedeagus V-shaped, median process triangular, tapering, aedeagal ratio ~0.3; parameres separate, major bend at close to middle of paramere, apex slender, posteriorly directed, with fringe of tiny hairs at tip. (Male genitalia most similar to Fig. 66 C . cockerellii.)

Distribution. Coastal Alaska, British Columbia, Washington, Oregon, California.

Larval ecology and life cycle. Williams (1951b) studied C. tristriatulus in Alaska and found the larval habitats to be tidally inundated marshes and stream banks characterized by sedge ( Carex Linnaeus [ Cyperaceae ]), with an average soil temperature of 13 °C, a pH of 6.2–6.6, and a larval density of up to ~1000/m 2. In the laboratory, ~15 d after blood-feeding, females laid 41– 81 eggs, which hatched within 10 h to 3 d at 18 °C. The species in univoltine, and larvae overwinter in the soil and pupate in the early summer. In the laboratory at 16–18 °C, the pupal stage lasts 7.5–9.5 d.

Adult behavior. Sailer et al. (1954) also studied C. tristriatulus in Alaska and found adult emergence in late July, with peak activity and formation of male swarms in the evening. Culicoides tristriatulus is a severe diurnal biting pest of humans ( Jenkins 1948; Williams 1951b; Sailer et al. 1956), with peak activity during low-light conditions in the morning and evening and a flight range of up to 8 km ( Williams 1951b).

Remarks. The Fish Creek Flats records reported by Wirth (1951) and larval habitat reports by Sailer et al. (1954) for C. tristriatulus are actually for Culicoides sommermanae Wirth and Blanton (Wirth and Blanton 1969) . I did not examine any C. tristriatulus .

Figures

Figures 117–125. Male wings of Culicoides subgenera Avaritia and Silvicola. 117) C. boydi (in grayscale) (Riverside County, CA [BM]). 118) C. obsoletus (MD [FSCA]). 119) C. cockerellii (Bonneville County, ID). 120) C. freeborni (San Diego County, CA [BM]). 121) C. lahontan. 122) C. neofagineus (in grayscale) (paratype, Mendocino County, CA [FSCA]). 123) C. neomontanus. 124) C. saltonensis (Imperial County, CA [FSCA]). 125) C. sierrensis (paratype, Modoc County, CA [FSCA]).

Figures 66–72. Male genitalia of Culicoides subgenus Silvicola, ventral view. 66) C. cockerellii (Bonneville County, ID). 67) C. freeborni (San Diego County, CA [BM]). 68) C. lahontan. 69) C. neofagineus (paratype, Mendocino County, CA [FSCA]). 70) C. neomontanus, basal and apical tips of aedeagus triangulated. 71) C. saltonensis (Imperial County, CA [FSCA]). 72) C. sierrensis (paratype, Modoc County, CA [FSCA]).