dcsimg

Conservation Status

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Unknown.
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Cyclicity

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Queens may be seen flying from late March to late October; males from late April to late September (Thorp et al. 1983).
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Distribution

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Western and eastern neartic regions (Williams 1998).
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General Description

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Bombus insularis belongs to the subgenus Psithyrus which was historically treated as a separate genus from the rest of the Bombus due to its parasitic lifestyle (Alford 1975). Michener (2000) considers all species formerly treated as Psithyrus to be Bombus. Psithyrusis a parasitic subgenus, and all species lack a worker caste, cannot produce wax, have a stronger exoskeleton, and have no pollen baskets (Alford 1975). Psithyrus males can be distinguished by an almost straight penis valve shaped like an arrow head; the hind tibia of Psithyrus queens is convex with a hairy outer surface (Williams 2008). Bombus insularis queens have yellow pile covering the mesopleura to the base of legs, dark venter, fourth antennal segments that are much shorter than the third or the fifth, and moderately stained wings (Franklin 1912). Bombus insularis can be distinguished from the closely related Bombus fernaldae by the presence of yellow hair between the antennal bases (Thorp et al. 1983). Queens vary in length from 13.5 mm to 18 mm; in wingspan from 32 mm to 38 mm; and in width of second abdominal segment from 7 mm to 9 mm (Franklin 1912).
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Habitat

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Found in a wide range of habitats due to its parasitic lifestyle (Alford 1975).
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Life Cycle

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Bombus insularis is a cleptoparasite of the nests of other Bombus species. Bombus insularis parasitizes at least 6 other Bombus subgenera (Thorp et al. 1983), an unusually large host range for the Psithyrus subgenus which normally specializes in a single subgenus (Alford 1975). Alford (1975) reviews the life history of B. insularis. Queens of B. insularis emerge later in spring than other Bombus queens and forage on pollen and nectar until a suitable nest to invade is found. Mature nests that were founded earlier in the year appear to be preferred, although entrance to the colony is normally easier if the colony is smaller. The queen enters the nest and will remain motionless with legs drawn in close if she is attacked. Upona successful entrance, the queen will hide for a short time, presumably to acquire the odor of the colony to avoid further attacks by workers. Sometimes B. insularis queens will kill the host queens, but often they are able to cohabitate. She will then construct her own egg cells and quickly lay eggs, sometimes feeding on the host brood. Her eggs and larva are reared by the host workers alongside the host brood. The newly emerged queens and males will immediately leave the nest to acquire mates. The B. insularis queen will then leave and seek out other nests to parasitize.
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Trophic Strategy

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Bombus insularis were observed foraging on 16 plant families with 30 genera in California. The predominant families fed upon were Compositae, Rosaceae, Ericaceae, and Polygonaceae (Thorp et al. 1983).
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Bombus insularis

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Bombus insularis is a species of bumblebee in the subgenus Psithyrus, the cuckoo bumblebees. It is native to northern and western North America, where it occurs throughout Canada, Alaska, the northern United States, and some western states. It is known commonly as the indiscriminate cuckoo bumblebee.[1][2]

The female of the species is 1.6 to 1.9 centimeters long and just under a centimeter wide. The head is black with tufts of yellow hairs and the thorax is coated in long pale yellow hairs. The legs are hairy black. The abdomen has is black with yellow along the sides. The male is smaller, about half a centimeter wide at the abdomen. The head has long black hairs with small patches of yellow and the abdomen has strips of yellow and black hairs.[3]

This species lives in tundra and taiga, western mountain ranges, and some maritime regions.[1]

As in other cuckoo bees, the queen of this species enters the nest of a host species, kills the resident queen, and lives and breeds in the nest tended by the host workers. Host species of this bee include the white-shouldered bumblebee (B. appositus), yellow bumblebee (B. fervidus), yellow-fronted bumblebee (B. flavifrons), Nevada bumblebee (B. nevadensis), and orange-belted bumblebee (B. ternarius).[1]

This bee is still common and widespread, though it has declined in some areas and disappeared from a few parts of its historical range. Some of its host species have faced more significant declines. Potential threats include habitat loss, pesticides, pathogens from domesticated pollinators, competition from introduced bees, and climate change.[1]

References

Wikimedia Commons has media related to Bombus insularis.
  1. ^ a b c d e Hatfield, R., et al. 2014. Bombus insularis. The IUCN Red List of Threatened Species. Downloaded on 08 March 2016.
  2. ^ NatureServe. 2015. Bombus insularis. NatureServe Explorer Version 7.1. Accessed 8 March 2016.
  3. ^ Bombus insularis. Mitchell, T. B. 1962. Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152. Reprinted at Discoverlife.org.
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Bombus insularis: Brief Summary

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Bombus insularis is a species of bumblebee in the subgenus Psithyrus, the cuckoo bumblebees. It is native to northern and western North America, where it occurs throughout Canada, Alaska, the northern United States, and some western states. It is known commonly as the indiscriminate cuckoo bumblebee.

The female of the species is 1.6 to 1.9 centimeters long and just under a centimeter wide. The head is black with tufts of yellow hairs and the thorax is coated in long pale yellow hairs. The legs are hairy black. The abdomen has is black with yellow along the sides. The male is smaller, about half a centimeter wide at the abdomen. The head has long black hairs with small patches of yellow and the abdomen has strips of yellow and black hairs.

This species lives in tundra and taiga, western mountain ranges, and some maritime regions.

As in other cuckoo bees, the queen of this species enters the nest of a host species, kills the resident queen, and lives and breeds in the nest tended by the host workers. Host species of this bee include the white-shouldered bumblebee (B. appositus), yellow bumblebee (B. fervidus), yellow-fronted bumblebee (B. flavifrons), Nevada bumblebee (B. nevadensis), and orange-belted bumblebee (B. ternarius).

This bee is still common and widespread, though it has declined in some areas and disappeared from a few parts of its historical range. Some of its host species have faced more significant declines. Potential threats include habitat loss, pesticides, pathogens from domesticated pollinators, competition from introduced bees, and climate change.

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