Trapdoor Spider

I found this beauty walking slowly across the leaves on the forest floor at Bull Mills.  It paid no attention to me until I put the camera on the ground 3" away and even then it only backed up an inch and posed.  I tried to get better pictures of its eyes but failed.  I decided to leave it rather than take it home for photographs.



This was identified as a Ummidia species, one of the Cork-lid trapdoor spiders (Ctenizidae).  Their diagnostic feature is the saddle-like depression in the outer surface of the tibia on their third leg.  Identifying the species would require an expert looking at other anatomical features.


They get their "trapdoor" name from the construction of their residence as described in Bugguide.

"Trapdoor spiders" because they make their homes in tubelike burrows completely lined with silk. They cut a lid which is attached on one side, like a hinged trapdoor. The top of the lid is camouflaged with debris. When they feel the vibration of prey, they rush out to capture it, then return to the burrow. Females rarely leave their burrows, but males may be found wandering in search of prey.

Note the two thick chelicerae which point down - REK

Ummidia sp were named for a famous Roman woman, Ummidia Quadratilla who unfortunately died 1900 years before she could learn of the honor.  These species are in the infraorder Mygalomorph, a group of stout bodied spiders that includes tarantulas.  Mygalomorphs have long stout chelicerae that point straight down.  Their chelicerae or jaws as they are referred to frequently are strong and  contain venom glands capable of killing fish and small mammals.  The only species that is a threat to humans resides in Australia.

There is only one species of tarantula that resides in Missouri, Aphonopelma hentzi.  In spite of their reputation in the popular literature, they pose no danger by biting and are frequently kept and handled as pets.  They do have urticating hairs that can cause irritation to sensitive eye and nasal tissue, so don't touch your eyes after handling them and never ever inhale a tarantula.

This video of petting a Missouri tarantula is not for arachnophobes. 
Trapdoor spiders