Thereva utahensis Hardy, 1938

Gibson, Joel F. & Cannings, Robert A., 2025, The Stiletto Flies (Diptera: Therevidae) of British Columbia, Yukon, and Alaska, Zootaxa 5618 (4), pp. 481-508 : 503

Thereva utahensis Hardy

Specimens examined (19). BC: Alexis Creek, Bull Canyon; Fernie, 10.7 miles W; Kinbasket Reservoir, Bush Arm; Osoyoos, Mount Kobau Road; Robson. YT: Alaska Highway, Christmas Creek, km 1688; Caribou Mountain; Carmacks; Klondike Highway, Moose Creek; Kluane National Park, Sheep Mountain; Minto; Nares Mountain ( Fig. 19 ); Whitehorse, Riverdale; White Pass, Log Cabin. DEBU, RBCM, ROME.

Database and literature records (71). BC: Atlin; Grand Forks; Hudson’s Hope; Kamloops; Keremeos; Lillooet; Merritt, Midday Valley; Mount Revelstoke; Osoyoos; Robson; Seton Lake; Taylor; Telegraph Creek. YT: Alaska Highway, 13.1 km W Takhini River ; Carcross; Christmas Creek, km 1688 Alaska Highway; Kluane Lake, Emerald Island; Kluane National Park, Mount Wallace; Kluane National Park, Sheep Creek Road; Kluane National Park, Sheep Mountain; Ross River; Stewart Crossing; Takhini; Tatchun Lake; Whitehorse. CASC, CNCI, LEMQ, MEI, SEM.

Conservation status. BC: S5. Yukon: S3S5

Distributional notes. Thereva utahensis is widespread in the British Columbia interior from the United States border north to Atlin and the Peace River region. It is common in the central and southern parts of the Yukon from Kluane Lake east to Carcross and Ross River, and north to the Stewart Crossing region. The species is probably distributed farther east based on locations in the British Columbia Peace River region.

Ecoprovinces and other designations. BC: Southern Interior, Southern Interior Mountains, Central Interior, Boreal Plains, Northern Boreal Mountains, YT: Boreal Cordillera.

Range. Cordilleran. Yukon, British Columbia, and Alberta south to California, Utah, and Colorado ( Webb et al. 2013).

Biological notes. Flight period: 4 June–26 September. Thereva utahensis lives in various habitats, including sand dunes ( Fig. 15 ), grasslands ( Fig. 19 ), and subalpine environments ( Fig. 17 ).

Figures

FIGURES 14–19. Representative habitats of species documented in this paper. Fig. 14. The unglaciated British Mountains west of the Firth River, Yukon, showing steppe grasslands and arctic tundra at the northern limit of trees in Canada. Dialineura gorodkovi and Psilocephala vicina have been collected here. Photo by Sydney Cannings. Fig. 15. Sand dunes at Bennett Lake, Carcross, Yukon, habitat for a diverse therevid fauna, including Cliorismia bussi, Dialineura gorodkovi, Pallicephala occidentalis, Pandivirilia conspicua, Psilocephala vicina, Spiriverpa albiceps, Thereva foxi, and T. utahensis. Photo by Sydney Cannings. Fig. 16. Tabuda planiceps habitat at Vaseux Lake, British Columbia; Pinus ponderosa trees with Purshia tridentata (green-leaved shrub) and Artemisia tridentata (grey shrub) in foreground. Photo by Robert Cannings. Fig. 17. Mount Kobau, British Columbia; view south to Osoyoos Lake.The grassland and subalpine slopes of this locality are home to Tabuda planiceps and at least four species of Thereva: T. aurofasciata, T. cingulata, T. fucata, and T. utahensis. Photo by Robert Cannings. Fig. 18. Upper beach at Cape Cook Lagoon, Brooks Peninsula, northwestern Vancouver Island, British Columbia—the only known Canadian locality for Thereva elizabethae. Photo by Robert Cannings. Fig. 19. The lower, south-facing grassland slopes of Nares Mountain, overlooking Nares Lake, Carcross, Yukon. Home of Thereva foxi and T. webbi. Photo by Sydney Cannings.