Mouse spiders (Missulena) are burrow-dwelling arachnids known for their robust build and specialized predatory lifestyle. They are active ambush hunters, relying on potent venom and intricate underground homes to capture and consume a diet tailored to their subterranean existence.
Characteristics and Habitat
The Missulena genus is primarily native to Australia, though one species inhabits Chile. These spiders are terrestrial and thrive in varied habitats, ranging from open forests and shrubland to areas near waterways and suburban gardens. Their survival depends on their ability to excavate burrows in the soil.
Mouse spiders exhibit pronounced sexual dimorphism, which often leads to the misidentification of the sexes as different species. Females are typically larger, stockier, and uniformly dark brown or black, spending nearly their entire lives within their burrows. Males are smaller but often display brighter coloration, such as the distinctive red head and jaws of the Red-headed Mouse Spider (M. occatoria). Both sexes possess a glossy carapace and large, bulbous chelicerae, which house their powerful fangs.
Prey Selection and Consumption
Mouse spiders are opportunistic predators; their diet is determined by what can be successfully ambushed from the burrow entrance. Their primary food source consists of various arthropods that wander within striking distance.
This includes:
- Ants and beetles.
- Other spiders.
- Scorpions.
- Centipedes.
While their diet is heavily skewed toward arthropods, mouse spiders occasionally consume small vertebrates. They have been documented preying on small frogs and lizards that pass too close to the burrow entrance. The spider uses its large, downward-pointing fangs and powerful venom to quickly subdue this diverse range of prey.
Once the prey is immobilized, the spider uses its powerful chelicerae to grasp the meal and drag it rapidly back down into the safety of the burrow. The venom ensures that even larger prey is quickly neutralized, preventing a struggle that could damage the burrow entrance.
Ambush Hunting and Burrow Design
The female’s burrow is a permanent residence, typically consisting of a vertical shaft that can extend up to 55 centimeters deep. The interior is lined with silk to stabilize the soil and provide a smooth surface, often including a side chamber where the female deposits her egg sac.
The most distinctive feature of the burrow is the specialized entrance, which is closed by a hinged trapdoor made of silk and soil. In some species, such as the Red-headed Mouse Spider, two surface trapdoors are constructed at nearly right angles to one another. This configuration increases the effective hunting area and the probability of intercepting passing prey.
The spider employs a sit-and-wait strategy, positioning itself just inside the entrance and sensing the environment for vibrations. Fine silk trip lines are sometimes placed radiating outward from the burrow lip to act as an early warning system. When a vibration signals potential prey, the spider launches a rapid strike.
Males’ hunting needs differ significantly from females. Upon reaching maturity, male spiders leave their burrows to wander extensively in search of females during the mating season. This wandering phase means they must occasionally forage for food outside the safety of their burrow, sometimes hunting on the surface at night.