EFFECTS OF PHOTOPERIOD AND PREY TYPE ON DIAPAUSE TENDENCY AND PREOVIPOSITION PERIOD IN PERILLUS BIOCULATUS (HEMIPTERA: PENTATOMIDAE)

Abstract

Attempts at using Perillus bioculatus (F.) for control of Colorado potato beetle, Leptinotarsa decemlineata (Say), have been hampered by an incomplete understanding of the predator’s over-wintering biology. This study determined the effects of photoperiod and life stage of prey (Colorado potato beetle) on tendency for adult females to enter reproductive diapause, duration of the preoviposition period, and mortality of females. Perillus bioculatus showed an increasing tendency to enter diapause rather than to initiate reproductive activities as day length decreased. Females that were fed large beetle larvae (mid to late fourth instar) showed a significant increase in the number of individuals entering diapause compared with females that were fed a mix of beetle eggs and small larvae (first to third instar). Probit analysis was used to estimate the photoperiod that caused 50% of females to enter diapause; these estimates were 15L:9D for females feeding on large larvae, and 14.5L:9.5D for females feeding on eggs and small larvae. Females that were fed large larvae also showed a longer preoviposition period and had a slightly significant higher rate of mortality than those fed eggs and small larvae.