Abstract
The life history of a stem-galling sawfly, Euura lasiolepis Smith, which attacks the arroyo willow, Salix lasiolepis Bentham, was studied during 1983 at Flagstaff, Ariz., at 2,132 m above sea level. Adults emerged from galls in May and June, and larval development was completed in October. Cocoons were spun in galls, in November and December, in which the larvae overwintered. Behavior of adults and development of immature stages are described. A survivorship curve shows that 42% of a cohort survive to the adult stage, 39% die in the egg stage, 17% are killed by natural enemies, and 2% die of unknown causes.