PUPATION SITE AFFECTS THE MATING SUCCESS OF SMALL BUT NOT LARGE FEMALE BAGWORMS, OIKETICUS-KIRBYI (LEPIDOPTERA, PSYCHIDAE)

In Costa Rican oil palm plantations, apterous female bagworms, Oiketic us kirbyi, emerge three weeks before and greatly outnumber males. Mati ng success of females is limited by the low abundance of males, as is obvious by the large proportion of females which never get mated durin g their lifetime. In the competition for access to mates, large rather than small females and females pupating on highest sites have a propo rtionately greater mating success. In the present study, we tested the hypothesis that pupation on highest sites represents a size-specific adaptation of small, least attractive females to increase their mating success. Small and intermediate-sized females had a higher mating suc cess on the apical than subapical section of upright leaves, whereas t heir mating success did not differ on the same two sections of horizon tal leaves. Equally high mating success of large females on apical and subapical sections of all leaves indicates that large females effecti vely attract males, independently of their pupation site. Enhanced mat ing success of small females on apical sections of upright leaves sugg ests that females compensate for small size by pupating in sites most suitable for attracting males. Lack of preponderance of small females on apical sections of upright leaves, however, invalidates the hypothe sis that pupation on higher sites represents a size-specific adaptatio n of small females to enhance their mating success. It suggests that s election of pupation sites by female larvae is influenced by additiona l factors other than mating success.