About Bombus crotchii Cresson, 1879
Crotch's bumble bee (Bombus crotchii Cresson, 1879) is a bumble bee species with a short to medium tongue length. It can be hard to distinguish from Bombus californicus and Bombus occidentalis, as all three share similar color patterns. Queen and worker female Crotch's bumble bees have black heads and thoraxes, with yellow markings on the anterior dorsal surface of the thorax, and occasionally yellow on the scutellum. On the abdomen, the first metasomal tergum (T1) is either entirely black, or black only across its middle portion. T2 is usually yellow, and sometimes black in its central area. T3 through T5 are either black or orange, while T6 is always black. Queens and workers have very similar coloration, differing primarily in body size: queens measure 23–24mm in length, while workers measure 14–18mm in length. Males have a slightly different appearance from queens and workers. They have very large eyes that cover most of their face, yellow facial hair, and a broad black stripe across the middle of the thorax. The front portion of the male abdomen is yellow, and the remaining abdomen is mostly black and reddish yellow. This species occurs primarily in California, United States. It is still present but uncommon in Baja California, Mexico, and extends north into Nevada. Most observed individuals of this species are found in coastal areas of southern California. The specific overwintering habitat of Crotch's bumble bee is not confirmed, but it is thought to share the typical overwintering behavior of other bumble bees, overwintering beneath leaf litter or in soft soil. Crotch's bumble bee lives in grassland and scrub habitats. It requires hotter, drier conditions than most other bumble bee species, and can only tolerate a very narrow range of climatic conditions. This species nests underground, most often in abandoned rodent dens, and it is nonmigratory.
