provided by University of Alberta Museums
Syrphus ribesii is oligovoltine in England, with either two or three generations per year, and overwinters as a cold-tolerant larva (Sadeghi and Gilbert 2000a). However, it has also been reported to migrate in large numbers to the Mediterranean to overwinter (Gilbert 1986). It is a common and voracious predator, and can have a significant effect on the natural regulation of aphid populations. Males can be heard to make an audible noise with their wings as they vibrate them rapidly to warm up their thoracic muscles for flight; this is presumably to maximize the chances of catching a female, as mating occurs mid-flight and lasts as little as two seconds (Gilbert 1986). After pupation, emerged adult females are able to oviposit 7 to 8 days post-eclosion (Sadeghi and Gilbert 2000b). Much work has been done on the oviposition preference of the females of this species, with females showing a strong preference to oviposit near sycamore aphids, rose aphids, and pea aphids when given a choice of eight species (Sadeghi and Gilbert 2000b). Many parasitoids of S. ribesii are also known, including (amongst many families) members of the Braconidae, Chalcididae, Proctotrupidae, Encyrtidae, and Ichneumonidae. In particular, the Ichnuemonid Diplazon laetatorius is a common enemy, and S. ribesii larvae have evolved many defences against them. The remain still when they detect parasitiod antennal tapping, and emit a sticky oral substance if an ovipositor is inserted. Finally, they will assume a crescent shape and roll over if an attack persists (Rotheray 1981).