Bombus caliginosus (Frison, 1927)

Bremus caliginosus Frison, 1927 : 376 [♂].

     Holotype ♂. USA, California, Arcata, 16 September 1920, by C.D. Duncan [INHS].

Bremus caliginosus var. tardus Frison, 1927: 380 [♂]. Synonymy by Stephen (1957: 100).

     Holotype ♂. USA, California, Carmel, 20 July 1921, by L.S. Slevin [CAS no. 2438].

Taxonomic notes: The ♀ was described by Stephen (1957: 102).

Frison (1927: 380) these taxa, both described from the male, were identical to B. vosnesenskii Radoszkowski, 1862 with respect to colour pattern, though differed in the longer malar spaces, the longer flagellomeres 3, 4, and 5, and the genitalia. He also recognized his variety tardus as differing from the typical form in having no pale pubescence on the metasoma, a colour pattern not depicted by Williams et al. (2014: 55); Stephen (1957: 102) examined the holotype and compared it to additional material from the type location – unable to find unbanded specimens, he indicated that the specimen represented a local variant and subspecies status was not justified. Thorp et al. (1983: 34) supported this, indicating that the colour pattern was likely unique to that specimen.

Others (Stephen 1957, Thorp et al. 1983; Williams et al. 2014) have all stressed the difficulty of distinguishing this species from B. vosnesenskii, especially females.

Biology: This species was reported using an above ground (ca 15 feet) bird nesting box by Pitelka (1954); though that author indicated that the queen may have overwintered in the nest box, there is no evidence to support it. Thorp et al. (1983) reported a surface nest in a garage that used cotton stuffing of a hammock for nesting substrate.

Distribution in Canada: Williams et al. 2014 [BC – southern Vancouver Island]; Sheffield and Heron 2019 [BC].