Mouse Spiders in Melbourne

How to identify a mouse spider

A mouse spider is a stout, heavily built, ground-dwelling spider between 10 and 35 millimetres long, with females noticeably larger and more solid than males. The feature to look for is the head: the Australian Museum describes a distinctively bulbous, shiny, very wide head and jaw region, with the eyes spread across the front of the carapace. Depending on the species, the abdomen is uniformly black, dark blue, or black with a light grey to white patch on top.

The male red-headed mouse spider is the one people remember. At around 15 millimetres he carries a bright red head and jaws against a gunmetal blue to black body, colouring so distinctive that identification is rarely in doubt. The female of the same species is a different animal to look at: up to 35 millimetres, uniformly dark brown to black, sometimes with a red tinge to the jaws, and built like a small tank. She spends her life in and around a burrow, which is why the mouse spiders people actually encounter are nearly always wandering males.

Mouse spider or funnel-web? Telling them apart

The two are confused in both directions, and Better Health Channel notes that mouse spiders are sometimes mistaken for funnel-webs. Three features separate them. The mouse spider's head and jaws are conspicuously bulbous and high; a funnel-web's carapace is glossy but lower and more even. The mouse spider's eyes are spread across the front of the carapace, where the funnel-web's eyes sit closely grouped. And the mouse spider's spinnerets, the finger-like appendages at the tail end, are short, where the funnel-web's largest pair is distinctly longer.

In practice the distinction changes little about what you should do. A stout, dark, burrowing spider that cannot be confidently identified deserves the cautious response either way, because the first aid for the two is identical. Where identification genuinely helps is on a property where burrows keep appearing: knowing which spider is digging them shapes the inspection and the treatment, and that is a job for someone who handles both species regularly.

Mouse spiders around Melbourne and Victoria

The Australian Museum recognises eight species of mouse spider, and two are of practical relevance in Victoria. The Atlas of Living Australia holds over five hundred Victorian occurrence records for the genus, the great majority of them the red-headed mouse spider (Missulena occatoria) and the eastern mouse spider (Missulena bradleyi). The red-headed species has the largest distribution of any mouse spider, found mainly west of the Great Dividing Range.

Habitat runs from open forest to semi-arid shrubland, and the Australian Museum records that red-headed mouse spider burrows are often dug into the banks of rivers, creeks and other waterways, with the species sometimes found in suburban gardens. Better Health Channel puts it plainly: mouse spiders are found all over Australia and may be found in suburban gardens. For Melbourne, that makes properties near creeklines, reserves and waterway corridors the most likely places to meet one.

The venom, the research and the first aid

The Australian Museum describes mouse spider venom as potentially as dangerous as that of the Sydney funnel-web, and Victorian health guidance lists the same envenoming picture for both: excessive saliva or tears, muscle twitching, breathing difficulty, a numb mouth and a racing pulse. The medical record puts that potency in proportion. A study in the Medical Journal of Australia reviewed 40 definite mouse spider bites from across the country and found one case of severe envenoming, a 19-month-old child who responded to funnel-web antivenom. Most of the 40 showed no envenoming at all, and the museum notes the spider is believed to use less venom and possibly even deliver dry bites.

The first aid is the funnel-web protocol, and both healthdirect and Better Health Channel name funnel-web and mouse spider bites as the two spider bites that call for it: apply a pressure immobilisation bandage firmly over the bite and up the whole limb, splint or otherwise keep the limb still, keep the person calm and motionless, and call 000. Funnel-web antivenom has proven effective in the rare severe mouse spider case, so hospital care covers the worst outcome. What the protocol asks of you is simply to act as though the bite is serious until a doctor establishes otherwise.

Burrows, lifecycle and the daylight wanderers

Mouse spiders are burrowers, and the burrow is a serious piece of construction: silk-lined and typically 20 to 55 centimetres deep. The red-headed mouse spider builds an oval entrance fitted with two surface trapdoors set almost at right angles to each other, thin and wafer-like on some burrows and thick plugs on others. The eastern mouse spider appears to dig a shallower burrow with a single flap-like door and a side chamber. From these hides the spider ambushes passing prey, mainly insects, along with other spiders and occasionally small vertebrates.

The lifecycle explains the encounters. Males take about four years to reach maturity, then leave the burrow to search for females, wandering in daylight from late summer through to early winter and especially after rain, which is unusual among this group of spiders and is why a mouse spider sighting is so often a midday one. Wandering males regularly fall into suburban swimming pools. Females lay 60 or more eggs in a sac inside the burrow; the spiderlings hatch over summer, stay with their mother into autumn, and in the red-headed species disperse by ballooning on silk threads, a rarity among burrowing spiders and the reason this one covers so much of the continent.

Reducing the risk at home

Around a Melbourne property the practical risk comes down to accidental contact with a wandering male or an unnoticed burrow. Through the wandering season, late summer to early winter, wear gloves for garden work near creeklines and waterway banks, check the bottom of the pool before reaching in, and shake out shoes, gloves and anything else left outside overnight. A spider found indoors or in the pool through those months should be assumed to be a wandering male and given the cautious treatment.

Burrows reward a careful eye, not a shovel. The trapdoors sit flush with the ground and are easy to miss, so if you find one burrow in a bank or garden bed, assume there may be others nearby and keep children and pets clear until the area has been looked at properly. Because females never travel, a burrow is a fixed, findable thing, and dealing with it is a matter of locating and treating the harbourage, not chasing a spider that has moved on.

Mouse spider FAQs