The Biology and Seasonal Development of the Vetch Bruchid, Bruchus brachialis Fahraeus, in Oregon1

Abstract

The first adults of the vetch bruchid (Bruchus brachialis Fahraeus) emerged from hibernation in the Willamette Valley of Oregon during the latter half of April of 1954 and 1955. Adults continued to emerge until field populations reached their peak in late May and the early part of June Mating occurred shortly after emergence and oviposition began when the first pods appeared on hairy vetch (Vicia villosa Roth) from June 10 to 18. Oviposition continued through July into the beginning of August, at which time most of the pods on vetch were mature. The field populations of adult bruchids declined steadily from the time of peak abundance until early August, when none were to be found. The eggs began hatching near the end of June and new larvae continued emerging until early August. The larvae penetrated the pods and began feeding within individual seeds. Larval development was evident within the seeds until late September. The first pupae appeared in mid-August, and the first new generation adults at the beginning of September. Newly emerged adults apparently sought hibernation sites soon after emergence, since they were rarely collected in the field, Many of the adults did not emerge from the seeds in the fall and remained alive in storage bins and granaries until the following spring.