Thereva webbi Holston & Irwin, 2005

Gibson, Joel F. & Cannings, Robert A., 2025, The Stiletto Flies (Diptera: Therevidae) of British Columbia, Yukon, and Alaska, Zootaxa 5618 (4), pp. 481-508 : 503-504

Thereva webbi Holston & Irwin

( Fig. 13 )

Specimens examined (28). BC: Whistler, Olympic Park. YT: Bear Creek Summit, Mt. Decoeli Trail; Caribou Mountain; Dempster Highway, North Fork Pass; Dempster Highway, km 562; Kathleen River; Klondike Hwy, Moose Creek campground; Kluane National Park, Kaskawulsh River. AK: Anchorage; Anchorage, Triangle Lake; Bettles; Fairbanks, Moose Creek Bluff; Matanuska. RBCM, ROME, UAM, SEM.

Database and Literature records (33+10). BC: Adams Lake; Atlin; Atlin, Warm Springs; Barkerville; Cathedral Provincial Park, Lake of the Woods trail; Chilkat Pass; Hope Mountains; Kamloops; Kaslo; Lisadele Lake ; Radium; Summit Lake , Mile 392 Alaska Highway. YT: Carcross, 3.2 km N; Haines Junction; LaForce Lake ; Minto Landing; Richardson Mountains , 66.03˚N; Teslin Lake , 16.1 km NW (type locality). AK: Cooper Landing ; Fort Yukon; Kenny Lake ; Matanuska ; Moose Pass ; Palmer ; Skagway ; Tazlina ; Valdez. CASC, CMVH, CNCI, EMEC, MEI, OSUC, ROME, SEM, UMSP, USNM, WSUC.

iNaturalist records (2). BC: Coppercrown Mountain (iNat 55120458). YT: Whitehorse (iNat 52909455, Fig. 13 ).

Conservation status. BC: S5, YT: S4S5

Distributional notes. Thereva webbi is widespread and common in the Interior of British Columbia from Chilkat Pass and Atlin east to Summit Lake (Alaska Highway) south to Whistler, Kamloops, Kaslo, and Radium. It probably occurs over the entire province in, and east of, the Coast Mountains. In the Yukon, the species is widespread and common from Haines Junction east to Teslin Lake, north to the northern Richardson Mountains, but is likely distributed over much of the territory. It is recorded from central (Bettles, Fairbanks) to southern (Anchorage, Kenai) Alaska.

Ecoprovinces and other designations. BC: Coast and Mountains, Southern Interior, Southern Interior Mountains, Central Interior, Northern Boreal Mountains. YT: Boreal Cordillera, Taiga Cordillera. AK: Beringia Boreal, Coast Mountains Boreal, Hypermaritime Forests.

Range. Boreal. British Columbia, Yukon, and Northwest Territories and east, in the far North, to Manitoba and Labrador; south in the West to Oregon, Utah, and Colorado ( Webb et al. 2013).

Biological notes. Flight period: 1 June–7 August. Thereva webbi lives in mixed and deciduous woodland as well as mountain and arctic tundra habitats ( Holston & Irwin 2005). In northern British Columbia, the species was found at Atlin, at warm springs in meadow/boreal forest habitat. In the Yukon, it was collected in Salix scrub, dry grassland slopes, and on dunes; in Alaska, on a lawn with Taraxacum plants and in black spruce muskeg with adjacent meadows and dry areas.

Figures

FIGURES 6–13. Selected species documented in this paper. Fig. 6. Acrosathe vialis male, Central Saanich, British Columbia, 21 June 2021 (iNaturalist 84506944). Photo by Thomas Barbin. Fig. 7. Pallicephala pachyceras male, Lake Cowichan, British Columbia, 24 June 2020 (iNaturalist 51032384). Photo by Brian Starzomski. Fig. 8. Psilocephala vicina female, Nahatlatch Provincial Park, British Columbia, 25 June 2021 (iNaturalist 97392001). Photo by Lena Chiasson. Fig. 9. Spiriverpa albiceps female, Cape Scott, Vancouver Island, British Columbia, 28 June 2020 (iNaturalist 57752358). Photo by Thomas Barbin. Fig. 10. Spiriverpa albiceps male, Teslin, Yukon, 31 July 2020 (iNaturalist 55078839). Photo by Jukka Jantunen. Fig. 11. Tabuda planiceps female, Kilpoola Lake area, Osoyoos, British Columbia, 23 May 2022 (iNaturalist 122086201). Photo by Brian Starzomski. Fig. 12. Thereva brunnea female, Tipella, Harrison Lake, British Columbia, 6 July 2020 (iNaturalist 53228675). Photo by Blair Dudeck. Fig. 13. Thereva webbi female laying eggs in the soil. Whitehorse, Yukon, 12 July 2020 (iNaturalist 52909455). Photo by Jukka Jantunen.