Trapdoor Spider, Cork-lid Trapdoor Spider
Ummidia species (likely Ummidia audouini)
Halonoproctidae (Trapdoor Spiders), Order Araneae. Characterized by heavy bodies and powerful legs built for burrowing.
Physical Description
A robust, Mygalomorph spider with a highly glossy, hairless cephalothorax and a velvety, duller abdomen. The body is thickset and low-slung, appearing very powerful for its size.
Size Estimate
Body length is typically 20-30mm (about 1 inch), with a leg span approximately the size of a quarter. This specimen appears to be an adult male searching for a mate.
Coloration & Markings
Predominantly jet black to deep chocolate brown. The cephalothorax is notably shiny and dark, while the abdomen is matte with a slightly greyer or brownish hue. No vibrant markings are present.
Web Type
The spider does not build an aerial web. It constructs a deep vertical burrow lined with silk and capped with a thick, camouflaged 'cork-lid' trapdoor made of soil and silk.
Eye Arrangement
A compact cluster of eight eyes located on a small mound (tubercle) at the front of the cephalothorax, typical of Mygalomorphs.
Leg Characteristics
The legs are thick, relatively short, and powerful. A key diagnostic feature is a saddle-shaped depression on the upper side of the third pair of legs.
Venom & Safety Information
Venom Information
The venom is primarily used to immobilize small invertebrates. It is not considered dangerous to humans though the large chelicerae (fangs) can cause a painful mechanical bite.
Medical Significance
Low medical significance. Bites typically cause localized pain, swelling, and redness similar to a bee sting. No systemic toxicity is expected. Standard wound care is recommended.
Safety Recommendations
These spiders are best moved outside using the 'cup and paper' method. They cannot climb smooth surfaces like glass well. Wear gloves if you must handle them directly to avoid a defensive bite.
Habitat & Behavior
Habitat & Range
Common across the Southern and Midwestern United States, including Oklahoma. They prefer woodlands, gardens, and lawns with stable soil for burrowing.
Behavior & Temperament
Generally shy and sedentary, spending most of their lives in burrows. Males wander during the rainy season or autumn to find females. They are not aggressive but may rear up in a defensive posture if cornered.
Diet & Prey
Ambush hunters that wait behind their trapdoor. They sense vibrations from passing insects, crickets, or beetles, then lunge out to grab and drag the prey into the burrow.
Seasonal Activity
Most active and visible during late summer and autumn in Oklahoma, particularly after rain when males emerge to search for mates.
Description
The Ummidia trapdoor spider is a glimpse into an ancient lineage of spiders. Often mistaken for tarantulas due to their heavy build, these spiders are master engineers of the soil. The males are most commonly encountered indoors when they accidentally wander in while searching for females during their seasonal 'walkabouts'.
Key Features
Glossy black cephalothorax, thick burrowing legs, and a distinct saddle-shaped indentation on the tibia of the third leg.
Similar Species
Often confused with Mouse Spiders (Scotophoeus) or small Tarantulas (Aphonopelma), but the hairless, shiny carapace and 'saddle' on the third leg distinguish Ummidia.
Life Cycle
Females can live for many years (over a decade) staying in one burrow. Males mature in 2-3 years and leave their burrows to find mates, often dying shortly after the mating season.
Ecological Importance
Vital for soil health and natural pest control, consuming terrestrial insects that many other predators cannot reach.
Conservation Status
Not listed by IUCN, but local populations are threatened by heavy tilling of soil, habitat fragmentation, and heavy pesticide use in lawns.
Interesting Facts
The 'cork' trapdoor is so well-camouflaged that it is nearly impossible to find when closed. These spiders can remain in the same burrow for their entire lives, lasting over 15 years.
Photography Tips
Focus on the glinting cephalothorax and the texture of the abdomen. A top-down shot is best for showing the thick leg proportions and the eye tubercle.
User Notes
This spider was on the couch at my house in Oklahoma. It’s the size of a quarter.
Identified: 2026-06-05T01:47:34.723940