October 2023 Spider of the Month

The October spider of the month (SOTM) is this front-eyed trapdoor spider (cf. Idiops sp.; Idiopidae) photographed by Kyle Thomas in Marloth Park, Mpumalanga.

In his original post, Kyle said:

“Had seen a bunch of these prickly little trapdoor spiders in their burrows beneath a tree but was never able to lure one out for photo. Surprisingly, after returning to them late in the evening, I saw a lone female wandering around outside and was finally able to get some amazing close-ups.”

Trapdoor spiders, like tarantulas, are mygalomorphs and are very different from araneomorphs (“normal” spiders). Instead of having only two book lungs, they have four, and instead of crossing fangs, their fangs point straight down. Their chelicerae also extend forwards. They also live much longer than araneomorphs. In fact, the oldest known spider was from this family – Number 16, a Gaius vilosus, was 43 years old when she was killed by a wasp.

Like all trapdoor spiders, they live in burrows. The females will often live their whole life in these burrows, while the males are often found wandering around, looking for females. The burrow is closed with a trapdoor that is camouflaged with material from the surroundings, such as sand, grass, or lichen, making these spiders very difficult to spot if they’re in their burrows. These trapdoors can be flat or cork-like. The burrows are mostly excavated during the rainy season, when the soil is soft. The spiders use the rastella (stiff spines on their chelicerae) to dig these holes.  

The name Idiopidae means “unique eyed” or “individual eyed”, from the Greek idios (unique/individual) and ops (eye). Unlike other trapdoor spiders, they have a pair of eyes on the front edge of the carapace, separated from the other eyes, making them quite easy to identify.

These spiders are mostly found in South America, Africa, and Australia, with a few occurring in South Asia. South Africa has 46 known species from six genera.