Cuterebra lepusculi Townsend parasitize cottontail rabbits (Sylvilagus nuttallii) in southern Idaho. Peak parasitism was 69% in mid-September. Mean development time in the host was 27 days. The species is univoltine in Idaho. Partially developed larvae were transferred from freshly killed to living hosts and the resulting larvae matured normally. Developing pupae were cooled or warmed to retard or speed development and synchronize adult emergence.