LIFE-HISTORY OF DISONYCHA-PLURILIGATA (COLEOPTERA, CHRYSOMELIDAE) AND HOST PLANT RELATIONSHIPS WITH SALIX-EXIGUA (SALICACEAE)

The life history of a chrysomelid leaf beetle, Disonycha pluriligata (LeConte), which lives and feeds on the coyote willow (Salix exigua Nuttall) was studied during 1987, 1988, and 1989 near Flagstaff, Ariz., at 2,132 m above sea level. We found that D. pluriligata is a univoltine insect which has three instars in overlapping succession with durations of 7, 7, and 48 d, respectively. Neither adults nor larvae are gregarious. Egg-laying and pupation occur in the soil, and insects overwinter in the adult stage. Seventy-six percent of all eggs laid in the laboratory hatched. Twenty-nine percent of a cohort survived to the adult stage when raised on female willow leaves, whereas only 18.5% survived on male willow foliage. The greatest mortality occurred just before pupation. Mating and feeding behaviors are described. D. pluriligata appears to be an eruptive species which may kill the willow ramets it feeds upon.