One of the coolest things ever discovered was that some flies are specialized parasitoids of crickets, and that the female flies find their cricket hosts by listening in on the calling songs of males (Cade 1975). It even made the pages of Olivia Judson’s ‘Dr. Tatiana’s Sex Advice to All Creation’. This puts male crickets in a bind: calling attracts females for mating, but also attracts a killer!
We have examined host specificity of different fly populations across the continental United States and Hawaii. Flies prefer their local host cricket song, but that preference is not absolute, and although the flies are quite specialized on field crickets, they show considerable plasticity in host finding behavior. This plasticity may have contributed to the spread of the fly throughout the warmer portions of North America, and facilitated its introduction to Hawaii, where it parasitizes Teleogryllus oceanicus, also introduced to Hawaii.
I am currently working with Marlene Zuk and Susan Balenger examining how genetic variation is partitioned among fly populations. We are using both mitochondrial DNA sequencing and microsatellite markers to estimate the population genetic history of the flies, and to identify the probable source population(s) for those flies introduced to Hawaii.
I am also gathering information on the known host species of O. ochracea in North America. At least 12 species of Gryllus are naturally parasitized. These 12 species have highly divergent song structures, from species with 2-3 pulses/chirp with slow pulse rates to species with long trills and fast pulse rates – and everything in between.
Papers about crickets and flies:
Paur, J. & Gray, D. A. 2011. Individual consistency, learning and memory in a parasitoid fly, Ormia ochracea. Animal Behaviour 82:825-830.
Paur, J. & Gray, D. A. 2011. Seasonal dynamics and overwintering strategy of the tachinid fly (Diptera: Tachinidae), Ormia ochracea (Bigot) in southern California. Terrestrial Arthropod Reviews 4: 145-156.
Sakaguchi, K. S. & Gray, D. A. 2011. Host song selection by an acoustically-orienting parasitoid fly exploiting a multi-species assemblage of cricket hosts. Animal Behaviour 81: 851-858.
Gray, D. A., Banuelos, C. M, Walker, S. E., Cade, W. H. & Zuk, M. 2007. Behavioral specialization among populations of the acoustically orienting parasitoid fly Ormia ochracea utilizing different cricket species as hosts. Animal Behaviour 73: 99-104.
O’Hara, J. & Gray, D. A. 2004. Two new Orthopteran hosts of North American Polideini (Diptera: Tachinidae). Entomological News 115: 171-172.
Gray, D. A. & Cade, W. H. 2000. Senescence in field crickets (Orthoptera: Gryllidae): examining the effects of sex and a sex-biased parasitoid. Canadian Journal of Zoology 78:140-143.
Gray, D. A. & Cade, W. H. 1999. Sex, death and genetic variation: natural and sexual selection on cricket song. Proceedings of the Royal Society of London, B 266: 707-709.