Observations on the Life History of the Horned Passalus

Abstract

Popilius disjunctus spends practically its whole life in rotting hardwood logs. The developmental history from egg to adult is completed in 21/2 to 3 months during the summer. There is but one generation per year. Each female lays about 30 large red eggs over a period of 2 or more weeks. The eggs change color and increase in size, weight, and water content during the 16 days required for their development. Approximately 12, 10 and 25 days, respectively, are spent in the three larval instars. A prepupal stage of 5 days and a pupal stage of 10-12 days are spent within the pupal case. The pupal case is made by the adults assisted from within by the larva. Food requirements, water relations, parasites and other animal associates, social life, and economic importance are discussed. The chief enemy of passalus is the parasitic fly, Zelia vertebrata, which causes the death of a third of the late third instar larvae.