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Two tachinid species discriminate between parasitized and non-parasitized hosts

López, Rolando, Ferro, D.N., Driesche, R.G.
Entomologia experimentalis et applicata 1995 v.74 no.1 pp. 37-45
Leptinotarsa decemlineata, Myiopharus doryphorae, growing season, hosts, larvae, larviposition, parasitoids, superparasitism
The abilities of Myiopharus doryphorae (Riley) and M. aberrans (Townsend) (Diptera: Tachinidae) to discriminate between parasitized and non-parasitized Colorado potato beetle (host) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) larvae, were investigated under laboratory and field conditions. Laboratory experiments showed that both Myiopharus species have a significantly greater frequency for larvipositing in non-parasitized hosts over parasitized ones. Direct field observations of larvipositional behavior of both Myiopharus species over three growing seasons showed effective restraint from larviposition into parasitized hosts, while larviposition into non-parasitized ones occurred readily. Avoidance of previously-parasitized hosts occurred after the larvipositing flies briefly landed on host larvae without attempting to insert the larvipositor. The low levels of superparasitism which occurred in the caged experiments and in the field appeared to be due to a breakdown of the larvipositing parasitoids' restraint when they met only parasitized hosts or when many parasitoids competed for reduced numbers of hosts late in the season.