2 MALE TYPES OF THE COMMON EARWIG - MALE-MALE COMPETITION AND MATING SUCCESS

A field-collected sample of earwigs (Forficula auricularia) showed con siderable variation and a bimodal distribution in male forceps lengths . Males could be separated into brachy types (74 %) with small forceps and macro types with long forceps. Female forceps lengths and the bod y length distributions of both males and females were unimodal. Staged encounters between males, matched for body size but of different forc eps type, demonstrated a significant advantage for macro males in aggr essive interactions. In experiments with more than one male together w ith a female, macro type males were able to dislodge and take over fem ales already in copula. Males of the macro type achieve both a larger proportion of the copulations and significantly longer copulations. Ex periments in the laboratory, where virgin females were placed in petri dishes with males of different types, revealed no difference in laten cy time to copulation. Neither was there any indication of female choi ce before copulation in experiments where females could choose between the two male types.