FITNESS DIFFERENCES ASSOCIATED WITH CALLING BEHAVIOR IN THE 2 WING MORPHS OF MALE SAND CRICKETS, GRYLLUS-FIRMUS

Alternate morphologies exist in a wide range of species. A commonly en countered dimorphism in insects is wing dimorphism, in which one morph is winged (macropterous=LW) and flight-capable while the other has re duced wings (micropterous=SW) and cannot fly. Gryllus firmus is a wing -dimorphic cricket found in the southeastern U.S.A. Although trade-off s associated with wing dimorphism are well established in female crick ets, no such trade-offs have been demonstrated in male crickets. Diffe rences between morphs in male G. firmus in the likelihood of attractin g a female were tested in the laboratory using a simple T-maze where f emales chose between an LW male and an SW male. Time spent calling for each male was recorded on the sixth day of adult life. SW males were more likely to attract a female and spent more time calling than LW ma les. A logistic regression of female choice against the absolute propo rtional difference in calling time between males revealed that, as the difference in calling time between males increased, the likelihood of a female choosing the longer-calling male also increased. Therefore i t is concluded that there is a trade-off between macroptery and the li kelihood of attracting a female, and that it may be a primary factor i n the maintenance of wing dimorphism in male G. firmus. (C) 1995 The A ssociation for the Study of Animal Behaviour