Triangulate Cobweb Spider, Triangulate Bud Spider
Steatoda triangulosa
Theridiidae (Cobweb Spiders), Order Araneae. Key family traits: messy tangle webs and 'comb-footed' tarsal bristles.
Physical Description
The spider has a distinct bulbous, globe-shaped abdomen and a smaller, slightly flattened cephalothorax. Its surface is smooth and glossy. The abdomen is significantly larger than the front section, typical of cobweb spiders.
Size Estimate
Estimated body length 3-6mm (1/8 to 1/4 inch). Leg span roughly 10-15mm. This specimen appears to be an adult female based on abdominal proportions.
Coloration & Markings
Features a brownish-purple to black cephalothorax. The cream or yellowish abdomen is decorated with a series of dark, purplish-brown zig-zag or triangular shapes connected along the midline, giving it its name.
Web Type
Tangle web or 'cobweb'. It is a messy, three-dimensional irregular lattice of silk, typically built in corners, under furniture, or near floorboards.
Eye Arrangement
Eight eyes in two rows of four. The eyes are small and fairly uniform in size, though not clearly visible without high magnification in this photo.
Leg Characteristics
Relatively long, slender legs compared to the body. They are translucent yellowish or pale brown with darker banding at the joints. Lacks heavy spines.
Venom & Safety Information
Venom Information
Contains theridiid venom, but it is not considered medically significant to humans. Potency is high for arthropod prey but weak for mammals.
Medical Significance
Harmless to humans. Bites are extremely rare and usually occur only if the spider is pinched. Symptoms are typically limited to mild local redness or swelling.
Safety Recommendations
No special safety measures are needed. If the web is bothersome, the spider can be safely relocated outside using a cup and paper, though it may not survive harsh winters outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Highly synanthrophic, meaning it lives almost exclusively around human dwellings, basements, and garages.
Behavior & Temperament
A shy, nocturnal, and non-aggressive ambush hunter. It remains in its web and will usually flee or drop to the ground ('play dead') if disturbed.
Diet & Prey
Generalist predator of ants, flies, beetles, and other spiders. It is notably known to prey on medically significant spiders like Brown Recluses and Black Widows.
Seasonal Activity
Active year-round indoors. In temperate climates, activity may peak in late summer and fall during mating periods.
Description
The Triangulate Cobweb Spider is a common household resident that acts as a silent guardian. While its messy webs may be an eyesore, it is a master hunter of household pests and even dangerous spider species.
Key Features
Triangular or zig-zag dark patterns on a pale bulbous abdomen; banded legs; small size; preference for dark indoor corners.
Similar Species
Steatoda grossa (False Black Widow) which is larger and darker, and the common House Spider (Parasteatoda tepidariorum) which has more mottled, less geometric patterns.
Life Cycle
Females produce white, textured, spherical egg sacs. Spiderlings emerge and often balloon to new locations. They can live for one to two years in sheltered indoor environments.
Ecological Importance
Provides excellent natural pest control within homes, specifically targeting 'pavement ants' and more dangerous wandering spiders.
Conservation Status
Not evaluated by IUCN; stable and abundant. It thrives in anthropocentric environments worldwide.
Interesting Facts
Despite its small size, it is a formidable hunter capable of taking down prey several times its weight by flinging sticky silk to entangle them from a distance.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen and the banding on the legs. Use a macro setting with a diffused flash to reveal the geometric shapes without glare on the glossy body.
Identified: 2026-06-02T01:48:40.534450