Assessment of aphid colonies by hoverflies. I. Maple aphids and Episyrphus balteatus (de Geer) (Diptera: Syrphidae)

In the syrphid hoverfly Episyrphus balteatus (de Geer), females in search of oviposition sites are assessing the qualitative and quantitative value of aphid colonies for securing the successful development of their offspring. They select small, young and "promising" aphid colonies consisting of nymphs and/or fundatrices as their oviposition sites, and neglect large, older ones including winged adults. Such "buy-futures" tactics will benefit the offspring in finding suitable and sufficient food.