Ummidia audouini

Order: Araneae
Suborder: Mygalomorphae
Family: Halonoproctidae

“My wife and I were on a nature walk when we saw what we thought was a large spider attempting to catch a big wasp.  It was a short fight that didn’t end like I thought it would.  Suddenly the spider quite fighting and became immobile.  After a brief rest, the wasp grabbed the spider by its fangs, drug it to a nearby hole and dropped it inside.  We continued our walk but the next day I went back to the site.  The spider was still inside the hole, which appeared to be lined with silk, and was still immobile, so I dug the whole thing up and brought it to you guys at Mississippi State.  What kind of spider is this and what kind of wasp could kill it?”

Trapdoor spiders are the closest thing we have to tarantulas here in Mississippi.  They are in the same suborder as tarantulas with which they share the trait of having fangs that point downward and are used in a stabbing motion, rather than the horizontally oriented pinching fangs of more evolutionarily advanced spiders.  There are only a few species of trapdoor spiders in the state, and U. audouini is the largest.  This spider has no common name, but members of this group are known as “cork-lid trapdoor spiders.”  Although their leg span is not as wide as some of our other large spiders, such as golden silk spiders, these chunky predators may well be our heaviest spiders.  This big female was 1.5 inches long.   

Trapdoor spiders live in silk-lined burrows they dig into the sides of hills or slopes.  They cover the entrance with a round, cork-like lid that has a silk hinge and is camouflaged with bits of soil and plant material.  This allows them to hunt by lying in wait under the partly opened lid and darting out to capture prey that ventures too close.  Female trapdoor spiders rarely leave their burrows and live for many years.  One Australian armored trapdoor spider was documented to live for 43 years.  Burrows of mature H. audouini females are approximately an inch in diameter.  These spiders have large fangs, but though painful, their bite is not considered seriously venomous to humans.

Trapdoor spiders have few natural enemies, but one family of wasps, known as spider wasps (Family Pompilidae), specialize in hunting and parasitizing spiders.  Tarantula hawks are large pompilid wasps that attack tarantulas, but it was likely a somewhat smaller species that was seen struggling with the mature female spider in the photo.  Spider wasps paralyze the spider with their sting, then place it back in its burrow before laying their eggs in the spider.

Never seen a trapdoor spider, or never even heard of trapdoor spiders?  Most people haven’t, and most people haven’t.  Their distribution in the state is not well-known because their habits, combined with that camouflaged trapdoor, make them hard to spot.  Males are seen more often than females.  The relatively short-lived males do not live in burrows as adults and are sometimes spotted wandering about over open ground in search of females.  If you do encounter trapdoor spiders in the state, we would appreciate hearing about it and seeing pictures.

Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
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