Triangulate Cobweb Spider, Triangulate Bud Spider
Steatoda triangulosa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Small, bulbous spider with a large, rounded abdomen and a smaller cephalothorax. The surface is smooth and slightly glossy. Females have a noticeably larger, more spherical abdomen than males.
Size Estimate
Body length is typically 3 to 6 mm. Including leg span, the spider reaches approximately 10 to 15 mm. The specimen in the image appears to be an adult female.
Coloration & Markings
Characterized by a brownish-black background with a distinct pattern of white or yellowish zig-zag/triangular markings along the dorsal midline of the abdomen. The cephalothorax is dark reddish-brown.
Web Type
Tangle web or 'cobweb.' Irregular, messy, non-sticky silk structures usually built in corners, under furniture, or near floorboards.
Eye Arrangement
8 eyes in two rows. The eyes are small and typical of the Theridiidae family, though not easily visible without magnification in this photo.
Leg Characteristics
Thin, spindly legs that are light brown or yellowish with darker banding or joints. The legs are relatively long compared to the body size, used for maneuvering in messy webs.
Venom & Safety Information
Venom Information
Contains various toxins used to paralyze insect prey. However, the venom is not medically significant to humans and is much weaker than its relatives in the Latrodectus genus.
Medical Significance
Harmless. Bites are rare and usually only occur if the spider is pressed against skin. Symptoms are typically limited to mild redness or localized pain similar to a bee sting.
Safety Recommendations
No special safety measures required. If unwanted, they can be safely relocated using a jar and a piece of paper. They pose no threat to pets or children.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Highly synanthropic, preferring indoor environments like basements, garages, and dark corners of houses.
Behavior & Temperament
Passive and reclusive. It remains in its web waiting for prey. It is not aggressive and will usually retreat or play dead (thanatosis) if disturbed by humans.
Diet & Prey
Generalist predator of small arthropods. Known to eat ants, silverfish, beetles, and even other spiders including brown recluse and black widow spiders.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though outdoor populations peak in late summer and autumn.
Description
The Triangulate Cobweb Spider is a common household resident often overlooked due to its small size and preference for dark corners. It is a master of the tangle web, acting as a natural pest controller.
Key Features
Triangular/diamond pattern on the dorsal abdomen, bulbous 'widow-like' shape but smaller size, and association with messy cobwebs in indoor settings.
Similar Species
Steatoda grossa (False Widow) which is darker and larger, and Latrodectus (True Widows) which lack the triangular dorsal pattern and possess an hourglass on the underside.
Life Cycle
Females produce round, white to tan papery egg sacs (one is visible above the spider in the image). They can live for one to two years and may produce several egg sacs in a lifetime.
Ecological Importance
Critical for indoor pest management. They help control populations of ants, cockroaches, and more dangerous spider species without the need for chemical pesticides.
Conservation Status
Not evaluated by IUCN; widely distributed and common with stable populations due to human habitation.
Interesting Facts
They are famous for 'widow-hunting'; they frequently prey on much larger and more venomous spiders, making them beneficial house guests.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen and use a macro lens or high-zoom setting to capture the zig-zag markings clearly. Use side-lighting to highlight the roundness of the body.
Identified: 2026-07-19T07:31:55.171567