Evaluation of the predatory hoverfly Eupeodes corollae (Diptera: Syrphidae) oviposition responses toward the aphid density and the presence of conspecific and heterospecific competitors

The choice of oviposition sites by hoverfly females determine the fate of offspring especially in those aphidophages whose newly hatched larvae have limited dispersal ability. This behaviour is influenced by several factors that their effects on oviposition behaviour of some species have received little attention. In this study we examined oviposition responses of the predatory hoverfly Eupeodes corollae to different sizes of aphid colony in three aphid-plant systems and to the presence of eggs or larvae of intra-or interspecific competitors in oviposition sites. Results showed that the predatory hoverfly females avoided laying eggs in aphid-uninfested plants. But in cases of availability of infested plants, they laid their eggs in proportion of aphid colony sizes. In response to presence of inter- or intraspecific competitors, females laid fewer eggs at sites where there were either larvae or eggs of inter-or intraspecific competitors. Moreover, it was shown that the presence of either larva of the heterospecific or conspecific competitor in the colony of the test aphid had stronger influences on oviposition avoiding of E. corollae females compared to the presence of either one day old egg of heterospecific or conspecific competitor. These findings may help to understand the mechanisms of decision-making by the ovipositing females of the E. corollae . However, a full understanding of oviposition responses of E. corollae as biocontrol agent of aphids to presence of inter-and intraspecific competitors in aphid colonies require follow-up research under field conditions. • Oviposition responses of E. corollae females toward different aphid densities as well as presence of intra-and interspecific competitors were evaluated. • The aphid species and the interspecific competitor used in our experiments were Aphis gossypii , Aphis craccivora , Macrosiphum rosae , and Coccinella septumpunctata. • The Negative binomial distribution showed that there is a positive correlation between the number of eggs laid by E.corollae and the aphid density in all three systems. • The adult female avoids laying egg on plant substrate which has a con-and hetero specific larva more than a con-and hetero specific egg. • The maximum avoidance of egg laying by the adult females, were observed in the presence of larvae of hetero specific competitor.