Ballarat's insects, spiders, scorpions and other wildlife are preparing for the winter chill

The persistence of flies and the presence of other insects such as fungus gnats and mosquitoes is not just a result of the ongoing warmer autumn, although the weather is a factor.

There is also evolution at play here, says Dr Ken Walker, senior curator of entomology at the Museum of Victoria.

The nub of the matter, he says, is some insects are better equipped by their evolutionary life-cycle to survive in cooler and cold weather.

Insects develop in one of three ways: the first and most ancient version is they are born as a tiny version of their adult self (silverfish are an example). This is ametabolism. Secondly, they are born, become a nymph and then an adult. This is hemimetabolism, and includes grasshoppers, cicadas, dragonflies, stinkbugs, cockroaches, and termites.

The third version is where the insect is born, then becomes a larva and pupa before metamorphosing into an adult. This is holometabolism, and it is a more successful adaptation to survival, says Dr Walker. Examples of holometabolous insects include flies, ants, bees, wasps, butterflies and moths, and beetles.

"The reason we think they are the most successful is when they are at different life stages, they have different food sources," Dr Walker says.

"Say you've got a butterfly. The caterpillar eats leaves and vegetation, while the adult only takes nectar for the carbohydrates and sugars to be able to fly. There's no competition between the different life stages for food.

"Whereas if you're a cockroach or a stick insect, then basically all stages of life are competing. So most of the successful insects, they spend the winter as either an egg or a pupa in a non-feeding stage, secreted very nicely on the bark of a tree or in between rocks or something like that.

"The large groups like the butterflies, the wasps, the bees, the flies, the beetles: these major groups use those four different stages, with two beautiful non-feeding stages."

Insects, spiders and scorpions are cold-blooded animals, unlike warm-blooded humans who need a constant source of food to produce enough heat to survive. Cold-blooded invertebrates don't need to generate heat, so don't have the same food requirements. When it gets really cold, they go to sleep; some of them will even make themselves a little doona, Dr Walker says. Just don't call it hibernation.

"Hibernation is more Northern Hemisphere attribute. When things freeze, the insects or invertebrates need to have some kind of almost anti-freeze in their body, so that the insect 'blood' or hemolymph doesn't actually explode when it's frozen," Dr Walker says.

"We don't really have those freezing temperatures here in Australia, so they go into a torpor or a stupor rather than a hibernation. On warm days, they will get out and try and feed, but really they are totally dependent on the ambient air to be able to warm their body up.

"One of the things you might find if you're looking at wood piles: this is where the queen European wasps spend the winter, hiding in wood piles. They sit there for the entire winter, waiting for spring. Another place you will find hibernating European wasps is inside the folds of curtains. Many a person has been stung by running their hand down or opening up a curtain; suddenly a queen European wasp has stung them."

For spiders and scorpions, more primitive predators in the evolutionary process, the last days of warmth are spent preparing for the privations of winter. Dr Walker says some spiders will weave what is essentially a silken sock or sleeping bag and go into a recess, finding what they 'hope' or perceive is a safe haven to live off body reserves as their metabolism slows.

'Hope' is in quotation marks because essentially, as far as science has been able to determine, invertebrates have very limited brain function, and spiders live with little more than a series of pre-programmed (though still highly complex) responses to stimuli. It's not to say they don't have brains - but to apply a mammalian concept of thought to insects and spiders is reductive, says Dr Walker.

"We don't know if they experience 'fear' for example, if they're threatened," he says.

"I would say they have an innate defence mechanism. That if, for example, a huntsman spider is threatened it will often rear up and try and bite. So initially they'll try a bit of a scare tactic by rearing up, and a lot of the huntsmen have markings on the underneath of their legs, and the markings often resemble eyes.

"If an animal sees another animal, it tries to work out its size based on its eyes, so it thinks it is much bigger. You'll often get this with praying mantis, their wings have spots on them, and moths. And what they're trying to do is to make their body look a lot bigger. Butterflies and moths in particular, when they're being attacked by a bird, a bird will always try and bite the head. So if you can present eye spots bigger than the head, the bird will go for the wing rather than the head.

"A lot of moths and butterflies can fly quite well, even though they've lost even up to half of their wings. So eyes spots are used a lot by invertebrates to make themselves look bigger, or to deflect predators away from where their actual head is."

One of the more interesting and brutal processes of the natural world is parasitism. Dr Walker says an effective winter hiding place is the best defence against hunters like spider wasps, which paralyse their prey with venom before laying eggs inside the host body, ready for them to devour from the inside out when they hatch.

"So the challenge for them is to find a place where they can hunker down for a months at an end and not get eaten or parasitised. It's quite a game of cat and mouse," Dr Walker says.

"Even the social huntsman spiders, Delena cancerides, they all hunker down together. They like to make themselves a silken bed. I've seen it many times: if you pull back bark, you will often see little strands and they make a little bed, like a doona, and then just basically all get together and sit very quietly while the cold months go through."

Another winter visitor to the indoors of peoples homes is the little marbled scorpion, Lychas marmoreus, which can make its way inside quite commonly on firewood. They are source of interest and fear to many, despite being only a couple of centimetres long.

"It's interesting: I get a lot of phone calls during the winter from people saying, 'There is a scorpion running across my floor, I've never seen it before.' And one of the questions I'll ask is, 'Have you got an open or wood fire?' Of course the scorpions are in the woodpile to get through the winter, and we bring them inside with the wood to be used in the fire.

"Inside the house is warm; the scorpion gets warmed up and goes roaming, goes walkabout. Of course they are venomous, but if you need to pick one up you can do it by the tail, you can quite easily use your thumb and forefinger. It's a bit like getting a cat or a dog by the scruff of the neck."

What we call 'European wasps' and 'huntsman spiders' and 'marbled scorpions' are the same creatures to Dr Walker, but he'll name them somewhat differently. As a taxonomist, he's responsible for issuing the Latin names which accurately classify our invertebrates. He stresses knowing what an invertebrate is accurately can assist in saving someone's life if they're affected by venom or allergy.

The process of classification is complex and there is a lot of Latin shuffling which takes place, but Dr Walker says it save a lot of confusion when there are so many derivatives of common names.

"Scientists generally despise common names," he says.

"There are so many different common names for the same scientific name.They almost become like a local tradition. And common names can be different. For example, there's one of the brown snakes in Western Australia, and there locally it's called a dugite. It's exactly the same bloody species.

"So the redback in Australia, the katipo in New Zealand and the black widow in the United States are all Latrodectus (Latin for 'small fangs'), but they are different species. By the way, the name 'small fangs' reminds us NOT to use a pressure mobilisation on a bite by a redback, because the venom is just under the skin, in the subcutaneous layer."

Useful to remember should you encounter the dreaded 'redback on the toilet seat'...