You’re almost certainly familiar with Hoverflies, which occur in most parts of the world. They are usually seen in poses like the one below, hovering near flowers (thyme in this case). This one is a Simosyrphus grandicornis, perhaps the most commonly found species in eastern Australia.
Hoverflies, or syrphid flies, are insects belonging to the Syrphidae family which is part of the order of true flies (Diptera). True flies, including hoverflies, differ from most other insects in only having one pair of wings (hence Diptera – two wings). The second pair has been reduced to small knobs called balancers. These are visible as cream-coloured protrusions just below the wings in the next photo.
Many hoverflies are useful pollinators, like the bees and wasps they resemble. They come in a variety of shapes and colours, most of them not greatly different from the one pictured above. Two other species are shown at the bottom of this post. .
Adult Hoverflies are typical insect imagoes, devoting most of their energy to feeding and breeding. They feed on pollen and nectar from the flowers they hover near. Mating is often done on the wing – hence my reference to the “mile-high club” in this post’s title. Here is a typical example, with the female enfolded in her mate’s embrace.
The offspring of this nuptial flight are small green maggots which are some of the most useful insect larvae in the garden. They are voracious predators of aphids and psyllids, and thus great rose-protectors. They move like leeches, raising their tapering heads and waving them around in search of their next prey. Once they latch on, they lift their prey clear of the leaf, and the aphid is doomed.
A hungry maggot can devour a decent-sized aphid in less than 20 minutes. The image above was taken at 9:24, and by the time of the next one below (taken at 9:28) the aphid had visibly deflated.
I took another at 9:36. Just as I did so, a breeze moved the twig a couple of millimetres, taking the duo out of the focal plane. Despite the resultant blurring, you can see that the aphid has been reduced to a shrunken corpse.
By the time the breeze stopped a few seconds later and I was able to refocus, the maggot had dropped the corpse. Job done!
Finally, here are a couple of different adult Hoverflies. This one with the rosemary flower has silver-and-black stripes instead of yellow-and-black, and a shiny gold thorax.
And this is an Australian Drone Fly (Eristalinus punctulatus), wiping down its slobbery-looking tongue with its front legs whilst sitting on a bloodwood bud. The Drone Fly is quite a bit larger than the other hoverflies I have shown, being about the size of a honey bee. Like the others, the adult Drone Fly feeds on pollen and nectar.