EFFECTS OF BODY-SIZE ON INVESTMENT IN INDIVIDUAL BROODS BY MALE PINE ENGRAVERS (COLEOPTERA, SCOLYTIDAE)

Large body size is generally associated with mating advantages and greater vigour in insects and other animals. Greater mating opportunities may favour reduced investment in individual broods, but greater vigour may contribute to greater brood success. To consider these issues, we examined the effect of body size of male pine engraver beetles, Ips pini (Coleoptera: Scolytidae), on the duration of paternal care and the reproductive success of their individual broods in a laboratory experiment. Larger males abandoned their mates and brood earlier than did small males. Nevertheless, larger males had more offspring and, when offspring emergence date was controlled by focusing on early emergers, larger males had larger offspring. There was no detectable effect of male size on the breeding behaviour of their mates. This study indicates that larger individuals realize higher fitness both through increased mating opportunities and through greater reproductive success in individual broods.