Single-colored Folding-door Spider, Turret Spider
Antrodiaetus unicolor
Antrodiaetidae (Mygalomorph spiders), Order Araneae. Key family characteristics include a specialized cuticular plate (sclerotized tergites) on the dorsal abdomen of males, orthognath jaws with parallel fangs moving vertically, and the construction of silk-lined burrows often featuring a hinged trapdoor or turret.
Physical Description
Robust, heavy-set body with a glossy, dark brown to black carapace and chelicerae. The abdomen is typically a duller brownish-grey or tan, covered in fine setae. It possesses large, powerful, forward-facing chelicerae characteristic of mygalomorphs.
Size Estimate
Body length ranges from approximately 10 to 20 millimeters (0.4 to 0.8 inches), with a compact leg span proportionate to its heavy body.
Coloration & Markings
Uniformly dark brown to glossy black cephalothorax and legs, contrasting with a lighter brownish-grey or tan abdomen. Lacks complex patterns or stripes.
Web Type
Does not build aerial webs. Instead, it constructs a silk-lined vertical burrow in the soil, often extending above ground as a mossy turret or sealed with a hinged trapdoor.
Eye Arrangement
Small eyes clustered tightly together on a distinct elevated tubercle (ocular prominence) near the front center of the carapace.
Leg Characteristics
Short, thick, powerful legs adapted for digging and gripping, heavily spined and covered in bristly setae, held close to the body in a compact stance.
Venom & Safety Information
Venom Information
Mygalomorph venom primarily used to subdue invertebrate prey. Not considered potent or medically significant to humans.
Medical Significance
Harmless to humans. While large individuals can deliver a mechanical pinch with their fangs, envenomation is rare, non-toxic, and causes minimal localized discomfort similar to a splinter.
Safety Recommendations
No special safety measures needed. Simply observe from a distance or gently relocate if found in an unwanted area by nudging into a container.
Habitat & Behavior
Habitat & Range
Found primarily in eastern and southeastern North America. Prefers damp deciduous forests, wooded hillsides, and shaded ravines with undisturbed soil.
Behavior & Temperament
A sedentary, highly secretive ambush predator that spends nearly its entire life inside its underground burrow. Generally docile unless severely provoked, but will rear up defensively with open fangs.
Diet & Prey
Insects and other ground-dwelling arthropods that pass within striking distance of the burrow entrance, which the spider ambushes from concealment.
Seasonal Activity
Most active during spring and summer. Adult males occasionally leave their burrows in autumn to search for females during mating season.
Description
The Folding-door Spider is a master of subterranean engineering. Rarely seen in the open, this stout, dark mygalomorph spends its days hidden within silk-lined burrows dug into forest floors. With glossy black mouthparts and a robust frame, it waits patiently at the threshold of its trapdoor or turret for unwary insects to pass, embodying the hidden biodiversity of woodland ecosystems.
Key Features
Glossy dark carapace, prominent forward-facing fangs (chelicerae), tight eye tubercle, and association with subterranean silk-lined burrows in forested habitats.
Similar Species
Can be confused with trapdoor spiders of the family Cictizidae or young tarantulas. Distinguished by the eye tubercle placement and specific habitat ranges.
Life Cycle
Females lay eggs inside their burrows and exhibit maternal care by guarding the egg sac and young spiderlings until they disperse to dig their own miniature burrows. Lifespan can span several years.
Ecological Importance
Serves as an important subterranean predator controlling ground-dwelling insect populations and contributing to soil aeration through burrowing.
Conservation Status
Not evaluated by the IUCN, but populations are locally secure in undisturbed forest habitats.
Interesting Facts
These spiders construct elaborate above-ground turrets made of silk, soil, and moss to camouflage their burrows and prevent flooding during heavy rains.
Photography Tips
Photograph from a low angle close to the ground using soft, diffused lighting to highlight the glossy texture of the carapace and chelicerae without causing harsh glares.
Identified: 2026-09-15T12:51:17.113344