Autumn common enquiries

Autumn weather supports a variety of wildlife for observation in our backyards and other natural habitats. The emergence of adult flies, millipedes and all the critters that live in the leaf litter are abundant in the rainy, windy months of the year.

Here are some of the most common enquiries we receive for animal identifications and explanations of animal behaviour.

This unusual-looking creature is a female Wingless Soldier Fly, Boreoides subulatus, affectionately known as a “walk” from its lack of wings. Without the need for wing muscles, these flies have more space for eggs in their abdomen, which increases in size as they get ready to lay. They can lay hundreds of eggs at a time. They may also look like they have a tail, but it is the organ they use to lay eggs (called an ovipositor). The males on the other hand look like other flies with a small size and working wings which they use to travel in search of females.

Wingless soldier flies are often found around compost and rotten logs as their larvae feed on decaying vegetation. The larvae are beneficial in this regard as they help to dry out the vegetation which lessens its smell, as well as making it less likely for other, more bothersome fly species to lay their eggs.

Whilst the flies are often spotted around compost heaps, the females don't lay their eggs there. Instead they usually find a tall vertical surface like a wall or fence to lay their large egg masses. It is around the autumn months that the eggs are laid, as the eggs are the only stage in their life that can survive the cold winter temperatures.

These larvae may look like caterpillars, but they are actually the larvae of sawflies which are related to wasps, bees and ants (order Hymenoptera). The larvae often move as a tight group of multiple individuals where they feed on eucalypts and related plants. They use the eucalyptus oil as a form of defence, dribbling it out when predators get close as the strong scent deters them. They will also raise their pointed tails up in the air as a group to make themselves look more threatening. This is largely a bluff since they do not have a damaging method of defending themselves.

These larvae can defoliate saplings and the lower branches of young trees in large enough groups, but usually the trees can recover if their canopy continues growing. You can find out more about these insects here.

Mygalomorph spiders encompass funnel-webs, trapdoors and mouse spiders, among others. These spiders are often dark-coloured, with thick, bulky bodies and large fangs which are parallel and oriented vertically. When threatened, they will rear up to strike downwards with their fangs.

During the warm, humid months from November to April, the males of funnel-webs and mouse spiders will leave their burrows and wander around in search of a mate (trapdoors will wander too, but they will do so throughout the year). This means they can be sighted more often and can sometimes venture into homes.

Trapdoor spider venom is not considered dangerous, however the venom of funnel-webs and mouse spiders is dangerous and medically significant. If you are bitten by a mygalomorph spider and are uncertain what type, use the pressure/immobilisation bandaging technique on the bite site, call for medical attention and if safely possible, capture the spider. You can learn more on how to differentiate the mygalomorphs on our funnel-web, mouse spider and trapdoor spider factsheets.

Millipedes belong to the subphylum Myriapoda, which roughly translates to “many feet”. The autumn months see Portuguese millipedes (Ommatoiulus moreleti) emerging from their summer underground to roam above the surface looking for mates.

Most millipedes are long, thin, segmented invertebrates with two pairs of legs on each body segment. Millipedes will curl up if disturbed. They are usually found in moist places such as under logs, rocks and in leaf litter. In gardens of any size these myriapods can be encountered under cushions, pot plants, rocks and washing baskets.

Millipedes feed on vegetable matter, leaf litter, moss, roots, new petals and leaves. They do not bite or possess a sting, though they can produce a fluid that can irritate eyes and can leave yellowish stains on clothing and skin. They can swarm in the hundreds and it is the autumn rains and the first growth of winter grasses that signal their return.

Like millipedes, centipedes are myriapods. Centipedes are larger than millipedes and have one pair of legs per body segment (as opposed to two pairs per segment in millipedes). There are over 125 species in Australia.

Centipedes are primarily predators, feeding on insects, snails, worms and even other centipedes. The first pair of legs are modified into claws with venom glands. The rearmost pair of legs are set backwards and are used for fighting off predators and holding prey. They also can look like antennae, confusing predators into attacking the wrong end.

Bites to humans are quite painful, but usually cause little more than a swelling of the local area. Centipedes are usually found in damp leaf litter, under rocks and logs, and in compost heaps. They sometimes enter houses, especially after rainfall has disturbed them from the garden.

You can learn more about centipedes and millipedes on our factsheet.

Many species of moths and butterflies are in their larval, caterpillar stage of their life cycle in the autumn months. They are very active in backyards, gardens and bushland habitats.

As caterpillars grow, they moult their exoskeleton multiple times. Each moult stage is called an instar, and it can have a different colour, pattern or texture to the last. This leads to a wide variety of caterpillar shapes and sizes. Usually they are identified by their adult stages since the larval stages can change so much.

See if you can spot any of these caterpillars in your backyard! You can learn more about caterpillars here.

If you have found an interesting critter in your backyard and would like it to be identified, you can contact our team using the "Ask an Expert" link below.