Hoverflies look very much like small wasps or bees but unlike these do not have a sting. These delicate insects are wonderful to observe in flight and a challenge to photograph.
Hoverflies, as the name implies, are flies. One thing that differentiates them from wasps and bees in that flies only have one pair of wings (wasps and bees have two pairs).
Pliny the Elder some 2000 years ago would have known this. Here is an extract from his Natural History.
There are some insects which have two wings, flies, for instance; others, again, have four, like the bee. The wings of the grasshopper are membranous. Those insects which are armed with a sting in the abdomen, have four wings. None of those which have a sting in the mouth, have more than two wings. The former have received the sting for the purpose of defending themselves, the latter for the supplying of their wants. If pulled from off the body, the wings of an insect will not grow again; no insect which has a sting inserted in its body, has two wings only.
Pliny the Elder (23-79 AD)
However, if you look carefully, you will notice a stick-like protrusion just behind the forewings - these are vestigial wings (also known as halteres). This is all that is left of what once was a second pair of wings.
