Triangulate Cobweb Spider, Triangulate Bud Spider
Steatoda triangulosa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A small spider with a bulbous, globose abdomen and a significantly smaller, flattened cephalothorax. The abdomen is glossy and smooth, while the legs are slender and lack heavy spination. Females are larger and more rounded than males.
Size Estimate
Body length typically 3-6 mm (1/8 to 1/4 inch). Leg span usually ranges from 12-20 mm. This specimen appears to be an adult female based on the prominent abdomen.
Coloration & Markings
The base color is brownish-black to purplish-black. The most striking feature is a pattern of white or yellowish zig-zag/triangular markings running down the center of the abdomen, bordered by dark pigmentation. The legs are typically light brown or yellowish with darker bands at the joints.
Web Type
Irregular, messy 'cobweb' or tangle web. Usually built in dark corners, crevices, or near the floor to catch crawling insects.
Eye Arrangement
Eight eyes arranged in two rows of four. The eyes are relatively small, which is typical for spiders that rely on web vibrations rather than eyesight for hunting.
Leg Characteristics
Legs are thin, tapering, and translucent in some lights. They feature tiny 'comb-like' hairs on the fourth pair of legs (tarsal comb) used for throwing silk over prey.
Venom & Safety Information
Venom Information
Contains various toxins but is not considered medically significant to humans. The venom is highly effective on small arthropods but lacks the necrotic or severe neurotoxic components found in Latrodectus.
Medical Significance
Low danger level. Bites are rare and usually occur only if the spider is pressed against the skin. Symptoms are minor, typically limited to local redness and slight swelling lasting a few hours.
Safety Recommendations
No special precautions needed. If relocation is desired, use a glass and paper to move the spider outdoors. They are beneficial to have in basements for pest control.
Habitat & Behavior
Habitat & Range
Found globally; common in North America, Europe, and Russia. It is almost exclusively synanthropic, preferring man-made structures like houses, basements, and garages.
Behavior & Temperament
Extremely shy and non-aggressive. They spend most of their time hanging upside down in their webs. If disturbed, they will usually retreat to a crevice or drop from the web on a silk line.
Diet & Prey
Generalist predators consuming ants, flies, ticks, and other spiders. They are known to hunt medically significant spiders like Brown Recluses and Redback spiders.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though sightings may increase in spring and autumn.
Description
The Triangulate Cobweb Spider is a master of the dark corners of human habitations. A member of the 'False Widow' genus, it is often overlooked due to its small size and preference for shadows. It serves as a natural pest controller, quietly cleaning homes of more intrusive pests.
Key Features
Distinctive zig-zag/triangular cream-colored pattern on a dark, glossy abdomen; dark banding on legs; irregular cobweb construction.
Similar Species
Steatoda grossa (False Black Widow) which lacks the triangular pattern, and Latrodectus (True Widows) which have a distinct hourglass on the underside and no triangles on top.
Life Cycle
Females produce round, white-to-tan papery egg sacs throughout the year indoors. They can live for one to two years. Spiderlings disperse via ballooning or crawling.
Ecological Importance
Significant household pest controller. They help regulate populations of ants, mosquitoes, and house flies within indoor ecosystems.
Conservation Status
Not evaluated by the IUCN; widespread and abundant with no known threats.
Interesting Facts
Despite its small size, this spider is a formidable hunter of other spiders, including the venomous Brown Recluse. It is one of the most common spiders found in households worldwide.
Photography Tips
Focus on the dorsal (top) side of the abdomen to capture the triangular markings. Use a macro lens or high zoom with good lighting to highlight the glossy texture and leg bands.
Identified: 2026-06-22T22:57:19.665213