Male crickets draw not only females with their songs but also parasitic flies. The uninvited guests then deposit larvae that burrow into their amorous hosts, grow for about a week and then tear their way out in "Alien" fashion, killing the cricket as they emerge.
Now, University of Florida zoologists have found that the danger posed by the flies has apparently affected when crickets sing. In experiments with Southeastern U.S. field crickets, known scientifically as Gryllus rubens, they discovered that considerably fewer male crickets sing in the autumn when the parasitic flies are abundant. They also found that female crickets are reluctant to approach singing males in the fall, perhaps unknowingly avoiding becoming the target of the flies themselves.
The findings, reported in a pair of recent papers in the journals Ethology and Animal Behavior, are of interest because they shed light on the interplay between the powerful evolutionary forces of sexual selection and natural selection, said UF zoology professor Jane Brockmann.
On the one hand, singing and finding mates increases a male’s reproductive success; on the other, it also carries high potential costs, Brockmann said. "The interesting question is how exactly do these conflicting pressures play out in evolution""
Scientists have known for some time that parasitic flies, known scientifically as Ormia ochracea, deposit larvae on, or near, singing crickets. The larvae burrow into the insects, then feed on nonessential organs within the cricket while they grow. After they emerge from the dying cricket, they pupate and metamorphose into mature flies.
Brockmann and co-author Manuel Vélez, a former UF student who earned his doctorate in 2004, hypothesized that the presence of flies would affect how male crickets sing and how females respond. Examining wild crickets native to North Florida, they devised
Source:University of Florida