Nest architecture

Many bumblebees are eusocial, similar to the eusocial Vespidae such as hornets in that the queen initiates a nest on her own rather than by swarming. Bumblebee colonies typically have from 50 to 200 bees at peak population, which occurs in mid to late summer.

Nest architecture is simple, limited by the size of the pre-existing nest cavity, and colonies rarely last more than a year.[37] In 2011, the International Union for Conservation of Nature set up the Bumblebee Specialist Group to review the threat status of all bumblebee species worldwide using the IUCN Red List criteria.[38]

There are many more species of primitively eusocial than highly eusocial bees, but they have been studied less often. Most are in the family Halictidae, or “sweat bees”. Colonies are typically small, with a dozen or fewer workers, on average. Queens and worke

rs differ only in size, if at all. Most species have a single season colony cycle, even in the tropics, and only mated females hibernate. A few species have long active seasons and attain colony sizes in the hundreds, such as Halictus hesperus.[39] Some species are eusocial in parts of their range and solitary in others,[40] or have a mix of eusocial and solitary nests in the sam

e population.[41] The orchid bees (Apidae) include some primitively eusocial species with similar biology. Some allodapine bees (Apidae) form primitively eusocial colonies