AbstractOf the 265 known bumble bee (Bombus) species, knowledge of colony lifecycle is derived from relatively few species. As interest inBombuscommercialization and conservation grows, it is becoming increasingly important to understand colony growth dynamics across a variety of species since variation exists in nest success, colony growth, and reproductive output. In this study, we reported successful nest initiation and establishment rates of colonies and generated a timeline of colony development for 15 western North AmericanBombusspecies, which were captively reared from wild-caught gynes from 2009 to 2019. Additionally, we assessed variation in colony size among 5 western North AmericanBombusspecies from 2015 to 2018. Nest initiation and establishment rates varied greatly among species, ranging from 5–76.1% and 0–54.6%, respectively.Bombus griseocollishad the highest rates of nest success across the 11-yr period, followed byB. occidentalis,B. vosnesenskii, andB. huntii.Furthermore, days to nest initiation and days to nest establishment varied among species, ranging from 8.4 to 27.7 days and 32.7 to 47 days. Colony size also differed significantly among species withB. huntiiandB. vosnesenskiiproducing more worker/drone cells thanB. griseocollis,B. occidentalis, andB. vancouverensis.Additionally, gyne production differed significantly among species withB. huntiicolonies producing more gynes thanB. vosnesenskii.Results from this study increase knowledge of systematic nesting biology for numerous western North AmericanBombusspecies under captive rearing conditions, which can further improve rearing techniques available to conservationists and researchers.