Yesterday, 17 March 2013, this harmless syrphid (A.K.A. flower fly) was hanging out in our
Twin Falls, Idaho backyard. For those of you who care about about such things: the eye is densely hairy – as a Scaeva eye should be. Syrphids are flies that get mistaken for bees and wasps by people, but one has to question what good that does? There are flies in the family Asilidae that mimic bees – because they (wolf-in-sheep’s-clothing) eat them! As people are finding more and more, the answers are probably species specific.
The reason for calling this post backyard predator – is this harmless fly is a voracious aphid-eating maggot (as are many syrphids). As do many (most?) holometabolous insects, the adult and larva do not compete with each other and utilize dramatically different resources – this is one of the reasons insects can be excellent bioindicators of ecosystem health. In this case, the presence of this adult means somewhere there are a lot fewer aphids.