Facultative Deposition of an Oviposition-Deterring Pheromone byHylemya1

Female Hylemya Sp.

Abstract

Hylemya Sp. (Diptera: Anthomyiidae) have been shown to oviposit on two species in the Polemoniaceae, Polemonium foliosissimum and Ipomopsis aggregata . Developing seeds of both species are utilized as a larval food. Previous work has demonstrated that an oviposition-deterring pheromone is deposited when an egg is laid on P. foliossissimum but that no such pheromone is secreted on I. aggregata . Reciprocal egg transplants were performed in the present study, and individual Hylemya females were demonstrated to be able to facultatively release an ovipositiondeterring pheromone. Egg mortality is greater on I. aggregata than on P. foliosissimum , making it unlikely that more than one larva will develop per I. aggregata flower. Pheromone is released only on P. foliosissimum , suggesting that females expend energy on pheromone release only in situations where competition for larval food is expected to be high.