The Mouse Spider is a member of the Trapdoor family. They are distinguished by the stocky body, long leg-like palps, and two knee-like lobes to which the fangs join in front.

At full size, the Mouse Spider are about the size of a 50c piece or 1 to 3 centimetres. They have short stocky legs with tiny eyes spread across the head. The Mouse Spider lives all over Australia but not in Tasmania. It lives in arid conditions as well as rainforests and bushlands. The home of the Mouse Spider is a burrow, oval shaped, of moderate depth and straight down. Female spiders spends all their lives in the burrow. Male spiders wander in Spring to Autumn. The burrow may be plastered with mud and digestive juices then lined with silk.

The females tend to remain in or near their burrows throughout their life, and are sluggish spiders that are rarely aggressive. However M. occatoria females have been found to produce copious amounts of highly toxic venom, which is potentially as dangerous as that of the Sydney Funnel-web Spider. Males wander during early winter, especially after rain. They will assume a threatening posture if disturbed. A bite should be treated the same as a funnel web bite and immediate first aid should be applied. Apply a pressure bandage over the bitten area as high up the limb as possible. Immobilise the victim. If possible, carefully collect spider for positive identification. Do not wash venom off the skin, as retained venom will assist identification.