Mating Behavior of Malacosoma Disstria at Two Levels of Mate Competition

Abstract

During a 3-year field study 2 levels of mate competition were observed in Malacosoma disstria Hubner, the forest tent caterpillar. Levels were indicated by the mean number per year of male attempts to mate females which were already in copula (interference rate). Sex ratio at emergence and population density probably determined interference rates. In the low level of mate competition, matings started late in the day and were short in duration, with some males terminating matings. In contrast, at the high level, matings began earlier and ended later with some females rejecting males and some males prolonging matings. The greater mate competition reflected a higher operational sex ratio, which probably increased the likelihood of some males finding females earlier and enhanced opportunities for females to be selective. Furthermore, the chance of sperm competition would be greater and prolonged matings were likely responses to this. Male terminated matings probably were responses to low chance of sperm competition.