Eat, Lay, Love – insects’ search for fulfilment

Life is simpler for insects than for us. Like us, they have to eat and reproduce. Unlike us, they don’t seem to want to achieve anything more than that, unless you count avoiding predators as an ambition.

These photos were taken in my garden at different times and don’t have much else in common except that their subjects are doing something more than merely resting.

Longicorn beetles (Cerambycidae) are usually identified by their exceptionally long, curved antennae. Their larvae are wood-borers and adults usually eat bark, although this one (probably a Double-coned Longicorn, Zygocera plumifera) seems to have no aversion to lichen.

longicorn beetle
Longicorn beetle eating lichen on a frangipani branch

When I started taking an interest in insects I quickly found that flies (Diptera) were far more numerous and more varied than I had guessed; better-looking and less harmful to us, too, if not positively beneficial. Many of them mimic colourful wasps, while many adults are nectar-feeders and some larvae are predators of plant pests.

The Soldier fly, Hermetia illucens, looks and behaves like a rather sleepy black wasp. Adults don’t feed at all, so they can neither bite us nor transmit diseases. The larvae are scavengers and decomposers, which makes the compost bin a particularly suitable place for the female to lay her eggs.

black fly
Soldier fly laying eggs under the lip of a compost bin lid

These lovers are also wasp-mimicking flies, Plecia amplipennis. They don’t really have a common name in Australia but are known overseas as ‘Love Bugs‘ for their habit of staying mated, like these two, for extremely long periods and even flying mated. When not engaged in this way, adults feed on nectar and pollen to keep up their strength.

black flies
Plecia mating on a bottlebrush twig

Microfauna (3) flies

When I started taking a real interest in invertebrates, flies were the group that surprised me most. Time after time, something I thought was a wasp or bee, even a dragonfly, turned out to be a fly. As the Queensland Museum says,

Flies belong to the Order Diptera. In Australia there are almost 7500 described species in 100 families. … Many sorts of insects are called flies but “true flies” are a distinct group of insects which have only one pair of wings, unlike the caddisflies, scorpion flies, mayflies and butterflies that have two pairs of wings. … True Flies are found everywhere, and include delicate craneflies, mosquitoes, and midges, as well as robust horseflieshouse flies and blowflies. …

If the stereotypical response to spiders is “Eeek!”, the response to flies is “Yuck!” Both responses are unfair, if only because of the enormous diversity of these families: many, probably most, of them are not at all scary and not at all disgusting in their habits. The QM again:

Biting, blood-feeding flies such as mosquitoes, midges, horseflies and blowflies are able to transmit diseases to humans and domestic animals. … But most flies are not pests, most are important decomposers of plant and animal matter.

This page doesn’t include any of the Diptera that we don’t usually think of as flies, e.g. mosquitoes and midges. None of them are as big as a house fly, which is 5 – 8 mm long, and most of them, like most of my tiny spiders and miscellaneous other tiny insects posted recently, are 2 – 5mm.  I don’t know much about some of the species pictured here, because they are so small they have escaped even my notice until recently, but I will give what information I can.

fat red fly with barred wings
Signal fly, Platystomatidae, Rivellia sp., about 4mm long.
slim brown fly with long legs
About 6-7mm long but very slim, probably a crane fly, Tipulidae. Resting on a Dianella lily.

Crane flies often don’t feed at all as adults, living only to breed. When they do feed, they feed on nectar. Bigger relations of this little one are very common, and here is a picture of one sipping from mango blossom.

Squat black fly with red eyes
Only about 2mm long but built like the proverbial Mack truck. Why? I don’t know. What is it? Ditto.
Colourful fly
2-3 mm long and strikingly coloured, and that’s about all I know.
metallic green fly with black-banded wings and abdomen
A Long-legged fly, Dolichopodidae, probably Austrosciapus connexus, about 4mm long.

The Long-legged flies are tiny counterparts to dragonflies in that they are swift, agile aerial predators. They are common in my garden year round but are very difficult to photograph because they are so fast – they usually jump at the beginning of the flash and show up as a blur on the edge of the picture. Dragonflies are not true flies, of course (they have four wings). One small indication of the diversity of our flies is that there are almost as many Australian species of this one family (about 320) as there are of all Australian dragonflies.

Most Dolichopodidae that I see are metallic green or gold, but some are less showy:

Long-legged grey fly
Dolichopodidae again, a little larger than the one above.

More about flies: CSIRO entomologyWikipedia/Fly.

Crane flies

Crane fly on mango blossom
Tiger Crane Fly, Nephrotoma australasiae, on mango blossom

Tiger Crane Flies are common in my garden all year round, their staggering flight from leaf to leaf distinctive enough that they are rarely confused with wasps even at a distance. Close up, of course, their extraordinarily long legs are unmistakeable.

But I had never really thought about what they live on – and the fact that they are flies doesn’t tell me a thing, since flies (Diptera) have diversified to live on nearly anything you can think of (and a few things we would usually rather not think of, for that matter). I have seen one apparently drinking from a drop of water on a leaf (see below) and this one on our mango blossom does seem to be drinking nectar, but almost every time I see them they are either in flight or simply resting on a leaf.

Wikipedia to the rescue: ‘Adult crane flies feed on nectar or they do not feed at all; once they become adults, most crane fly species exist as adults only to mate and die.’ (That must explain why I so often see them mating. Here is a picture of a mating pair.)

Wikipedia continues: ‘Female abdomens contain eggs, and as a result appear swollen in comparison to those of males. The female abdomen also ends in a pointed ovipositor that may look somewhat like a stinger, but is in fact completely harmless. Their larvae, called “leatherjackets”, “leatherbacks”, or “leatherjacket slugs” because of the way they move, consume roots of turf grass and other vegetation, in some cases causing damage to plants.’

Cranefly drinking from water droplet on leaf
Cranefly drinking water from the surface of a leaf