In experiments using sets of 12 individually caged male field crickets (Gryllus veletis and G. pennsylvanicus) suspended above pitfall traps in an outdoor enclosure, each male attracted zero-nine females over a 4-day period in which 48-60 females were released. Male age was significantly positively correlated with the number of females attracted in both species, whereas male body size, time spent calling and level of infestation with gregarines (protozoan gut parasites) were unrelated to male attractiveness. Older male G. pennsylvanicus (at least 15 days past adult moult) also attracted significantly more females than did younger males (7-9 days after adult, moult) when pitfall traps and cages were set in the field, allowing naturally occurring females to fall into the traps. Because males were kept from contacting each other in the experiments examining correlates of attractiveness, females appeared to be actually choosing older males, rather than indirectly relying on the results of male-male competition.
Bibliographical noteFunding Information:
I thank the members of my doctoral committee: R. D. Alexander, W. H. Cade, W. G. Holmes, P. R. Grant, P. Smouse and especially W. D. Hamilton, for their advice and comments on the manuscript and with my research. The comments ofW. Loher and an anonymous reviewer were also very helpful. S. Fleenor gave useful field assistance, and J. T. Rotenberry provided statistical and other help. My research was supported by the Walker-Hinsdale fund of the Museum of Zoology, the Division of Biological Sciences, the Horace H. Rackham School of Graduate Studies and the University of Michigan Biological Station.