As of September of 2022, Crotch’s bumble bee (Bombus crotchii), western bumble bee (Bombus occidentalis), Franklin’s bumble bee (Bombus franklini), and Suckley’s cuckoo bumble bee (Bombus suckleyi) became the first insect species to become candidates for listing under the California Endangered Species Act (CESA). They are protected by the same take prohibitions given to species listed as endangered and threatened under CESA. On July 24, 2026, the California Department of Fish and Wildlife published the "Considerations for Conserving Crotch’s Bumble Bee (Bombus crotchii), Franklin’s Bumble Bee (Bombus franklini), Western Bumble Bee (Bombus occidentalis), and Suckley’s Cuckoo Bumble Bee (Bombus suckleyi)" (PDF). This document is a non-regulatory resource for CDFW staff, consultants, project proponents, land managers and other interested stakeholders with information on the biology, ecology, habitat requirements, and seasonal life history of these four candidate bumble bee species along with example avoidance and minimization measures that may help support project planning and habitat stewardship.