THE EVOLUTION OF OVIPOSITOR LENGTH IN THE PARASITIC HYMENOPTERA AND THE SEARCH FOR PREDICTABILITY IN BIOLOGICAL CONTROL

John Sivinski and Martin Aluja

Abstract


Ovipositor lengths are thought to reflect the egg-laying and host-searching behaviors of parasitoids. For example, parasitoids that attack exposed foliage feeders often have short ovipositors compared to species that must penetrate a substrate to reach a host. However, the relationship between host accessibility and ovipositor length is not apparent in a guild of braconids that oviposits in the larvae of frugivorous Mexican tephritids. While the longest ovipositors are up to 5× longer than the shortest, all attack roughly the same stages of their shared hosts, often in the same fruits. Nor is there any evidence that the shorter ovipositors represent a saving of metabolic resources and energy that is redirected toward egg production or greater ability to move. It has been suggested that if the ovipositor length of an introduced parasitoid is substantially different from the ovipositors of species already present, then it is more likely to find an empty niche in its new environment, become established, and add to the control of its host. However, with the present lack of a simple explanation for the variety of ovipositor lengths within the Mexican guild it is not clear how predictive ovipositor length would be in this instance. Until the evolution and maintenance of the various lengths is better understood it may be more circumspect to practice fruit fly biological control through the conservation and augmentation of parasitoid species already present.

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