Nutrition
Eristalis transversa’s are carnivores and herbivores. In adult form, E. transversas are herbivores. They can be seen hovering from flower to flower, thus the name hover or flower fly, feeding on pollen, nectar or honeydew produced by aphids, some of their main food sources. Nectar from flowers give Syrphidaes flies the nutrition to sustain flight in midair while pollen assists female flies with their production of eggs in the ovary.
The environment at which the eggs are laid contributes to their diet. Compared to the adults, the larvae are carnivores and have a much more diverse diet. Some Syrphidae eggs are laid within beetles where they eventually hatch to drain the host’s egg(s) dry. McGavin says that the diet of the Syrphidae’s larvae consists mainly of aphids and other soft bodied insects, but may also include (McGavin 2002):
·
soft bodied insects
·
dung
·
mud
·
stagnant water
·
plants/buds
·
fungi
·
decaying matter/wood
and dead larvae
Photo by Jack
Kelly Clark, used with permission from the University of
California Statewide IPM Program
Aphids on a leaf, one of Eristalis transversa's main
food sources
So, it would be uncommon to see Syrphidae larvae plowing through an aphid colony. Because, aphids aid Syrphidae larvae as they develop into the pupas, it’s averaged that the amount of aphids consumed is a staggering amount of 300 aphids, and all of this takes place within seven to ten days. The eating process of hover fly larva can be referred to spiders in the class Arachnida. Swan and Papp clarify this process, “Aphid-feeders-they are usually pointed at the head-grasp the prey with their jaws, rise it into the air, and drain the body contents” (Swan and Papp 1972).
Learn about how hover flies reproduce: Reproduction