Red-headed Mouse Spider

Introduction

When the species was first described males and females were treated as two different species due to their vastly different size and appearance. It wasn't until years later that researchers found a mating pair that they were in fact the same species.

Why 'mouse' spider? Several possible explanations have been suggested

• someone found a spider in a deep burrow that had possibly been an old beetle or mouse hole.
• they are alleged to eat mice
• the large females resemble mice

Identification

Red-headed Mouse Spiders have a smooth, glossy carapace and their head area is high, steep and broad with very large, bulbous jaws. Their eyes are widespread across the front of their head. The spinnerets, at the back of the abdomen, are short and blunt, the last segment domed and button-like.

Female Red-headed Mouse Spiders are large, stout spiders with short legs. They tend to be uniformly dark brown to black all over, however their jaws are sometimes red-tinged. Female Red-headed Mouse Spiders are much larger than the males.

Male Red-headed Mouse Spiders have a bright red head and jaws and a gunmetal blue to black abdomen. They have thinner and longer slender legs without mating spurs. They are much smaller than the females.

When the species was first described males and females were treated as two different species due to their vastly different size and appearance. It wasn't until years later that reasearchers found a mating pair that they were in fact the same species.

Like the trap-door spiders, the mouse spider lives in burrows in the ground, often in banks of rivers, creeks and other waterways, and is sometimes found in suburban gardens. The burrows are built with double or single trapdoors and the entrance is oval-shaped. Some species have a side chamber extending of the main burrow shaft, usually closed by a trap door. It provides a refuge from predators and a safe place for the egg sac and spiderlings. The burrow can extend for a depth of about 30cm - which is unusually deep for a spider, but not as deep as previously claimed for this species.

Red-headed Mouse Spiders can be found in open forest to semi-arid shrub-land habitats.

The females tend to remain in or near their burrows throughout their life, and are sluggish spiders that are rarely aggressive.

Distribution

Red-headed Mouse Spiders (Missulena occitoria) have the largest distribution of all the Mouse spiders. They are found across mainland Australia, however mainly west of the Great Dividing Range.

Seasonality

The male Red-headed Mouse Spiders are usually found wandering for females during the day in late summer (Feb)to early winter months (Jun). They tend to be more common especially after rain. Females remain in their burrows.

Feeding and diet

Red-headed Mouse spiders mainly prey on insects and other spiders, but also occasionally on small vertebrates such as frogs and lizards.

Other behaviours and adaptations

Female Red-headed Mouse spiders have been found to produce copious amounts of a highly toxic venom, which is potentially as dangerous as that of the Sydney Funnel-web Spider.

Breeding behaviours

Males reach sexual maturity at about four years. They leave their shallow burrows during the breeding season to find a mate. They are unusual in that their wandering behaviour occurs during the day, unlike other mygalomorph spiders, whose males are night wanderers. While wandering, male mouse spiders hold their long pedipalps (carrying the mating organs) extended forwards, presumably seeking an airborne scent (pheromone) associated with the femaleor its burrow. Once the burrow is located the male taps the ground and silk around the doors until the female emerges. If she is receptive the male follows her into the burrow where mating occurs.

The female lays 60 or more eggs within an egg sac that she places into a brood chamber off the main shaft of her burrow. The spiderlings hatch from the egg sac over summer and remain with the mother into autumn when dispersal occurs.

The spiderlings of the Red-headed Mouse Spider disperse by ballooning, a technique that is rare in mygalomorphs. This explains the relatively wide distribution of Red-headed Mouse Spiders compared to other mygalomorph species.

Predators

Predators of the Red-headed Mouse Spider include parasitic wasps, bandicoots, scorpions and centipedes.

Danger to humans

Mouse Spider venom may be very toxic, but few cases of serious envenomation has been recorded. Other bites have occurred causing minor effects. Funnel-web spider antivenom has proved effective in the one confirmed case.

Until more toxicity data is available it is prudent to treat as for Funnel-web spider bite, especially if the victim is a child. Apply a pressure bandage over the bitten area as high up the limb as possible. Immobilise the victim. Collect the spider for positive identification. Do not wash venom off the skin, as retained venom will assist identification.

References

• Brunet, B. 2008. Spider Watch: A guide to Australian spiders. Reed New Holland.
• Simon-Brunet, B. 1994. The Silken Web: a natural history of Australian Spiders.Reed Books.
• Sutherland, S.K. & Nolch, G. 2000. Dangerous Australian Animals. Hyland House.
• York Main, B. 1976. Spiders. Australian Naturalist Library, Sydney.