The mouse spider (Missulena) is a significant Australian arachnid often mistaken for the more notorious funnel-web spider. These mygalomorphs are recognized for their robust body structure and distinctive appearance. They are named for the long-disproven belief that they dig deep, mouse-like burrows. Mouse spiders are widespread across the continent, and understanding their characteristics and habitat is important.
Geographical Distribution Across Australia
Mouse spiders are endemic to Australia, meaning they are native to and found almost exclusively on the continent, with the exception of a single species in Chile. The genus Missulena is widely distributed across mainland Australia, thriving in diverse environments from coastal regions to arid inland scrublands. Different species are specialized to various regions, resulting in their presence in nearly every state.
The Red-headed Mouse Spider (Missulena occatoria) is widely distributed throughout mainland Australia, mainly found west of the Great Dividing Range. Conversely, the Eastern Mouse Spider (Missulena bradleyi) is concentrated along the east coast, ranging from Queensland down to Victoria and parts of South Australia. Other species, such as the Northern Mouse Spider (Missulena pruinosa), are found in regions like the Northern Territory and Queensland.
Habitat and Burrow Construction
Mouse spiders are terrestrial and spend most of their lives in subterranean burrows constructed in soil. They prefer habitats ranging from open forests and woodlands to suburban gardens, often selecting spots near waterways. The burrows are typically deep, extending up to 30 centimeters (12 inches) or even 55 centimeters in some species, and are lined with silk for stability.
A defining feature of the mouse spider’s home is the entrance, which is usually covered by one or two hinged, oval-shaped trapdoors. These lids are constructed from a blend of silk and soil, making them difficult to detect. The trapdoor serves as an ambush point for the spider to wait for passing prey. The burrow provides a stable refuge for the female from predators and harsh environmental conditions, such as low humidity and high temperatures.
Key Characteristics for Identification
Mouse spiders are medium-to-large mygalomorphs, with body lengths typically ranging from 1 to 3.5 centimeters. They possess a robust, stocky build and a glossy carapace, featuring a high, broad head region. Their eyes are spread out across the front of the head, which helps distinguish them from other trapdoor spiders.
Pronounced sexual dimorphism is a significant feature. Females are generally larger, stouter, and uniformly black or dark brown, rarely leaving their burrow. Males are smaller and exhibit brighter, species-specific color patterns, making them more frequently encountered when wandering in search of mates. For instance, the male Red-headed Mouse Spider has a bright red-tinged head and jaws with a gunmetal blue abdomen. The Eastern Mouse Spider male has a distinct bluish patch on its abdomen.
Understanding Mouse Spider Bites
The mouse spider’s venom is potent, containing toxins similar to those found in the highly dangerous funnel-web spider. Although the potential for serious envenomation exists, few cases of severe systemic effects have been recorded. This is possibly because the spider often delivers a “dry bite” or only a small amount of venom. Symptoms of a significant bite can include severe local pain, sweating, nausea, vomiting, and muscle twitching.
For any suspected bite by a large, black spider, medical assistance should be sought immediately, as mouse spiders are often confused with funnel-webs. The recommended first aid is the Pressure Immobilisation Technique (PIT). PIT involves firmly wrapping a broad elastic bandage around the bitten limb and immobilizing it with a splint. The antivenom developed for the Australian funnel-web spider has been shown to be effective in treating serious mouse spider envenomation.