Triangulate Cobweb Spider, Triangulate Bud Spider
Steatoda triangulosa
Family Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A small spider with a bulbous, globose abdomen and a much smaller, reddish-brown cephalothorax. The abdomen is notably shiny and somewhat translucent, typical of the cobweb spider family. Females have a larger abdomen, while males are smaller and more slender.
Size Estimate
Adult females range from 3 to 6 mm in body length; males are slightly smaller at 3 to 4 mm. Total leg span is generally under 15 mm.
Coloration & Markings
Distinctive brownish-purple or mahogany zig-zag or triangular patterns running down the center of the abdomen against a pale cream or yellowish background. The cephalothorax is brownish-orange, and the legs are yellowish with darker bands at the joints.
Web Type
Irregular, messy 'cobwebs' or tangle webs built in dark corners, often near the floor. These webs are not ornate but are highly effective at trapping crawling insects.
Eye Arrangement
Eight eyes arranged in two rows of four. The lateral eyes on each side are usually touching or very close together, a characteristic trait of Theridiids.
Leg Characteristics
The legs are relatively long and thin. The fourth pair of legs (hind legs) features a row of slightly curved serrated bristles called a 'comb-foot,' used to wrap silk around prey.
Venom & Safety Information
Venom Information
The venom is not considered medically significant to humans. While it contains toxins to paralyze insects, it is not potent enough to cause serious harm to people or pets.
Medical Significance
Harmless. Bites are extremely rare and usually occur only if the spider is pressed against the skin. Symptoms are typically limited to mild, localized pain and slight swelling similar to a bee sting.
Safety Recommendations
These spiders are best left alone as they eat household pests. If relocation is desired, use a jar and a piece of paper to move the spider outside or to a garage. No special first aid is usually required for bites other than cleaning the site.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution found globally. It is predominantly a synanthropic species, meaning it is commonly found in and around human dwellings, basements, garages, and crawl spaces.
Behavior & Temperament
A shy, nocturnal hunter that stays within its web. It is extremely non-aggressive and will typically retreat or drop from its web if disturbed. It spends the day hiding in a retreat near the web's edge.
Diet & Prey
A generalist predator of small arthropods. It is known to eat ants, beetles, flies, and even other spiders, including species larger than itself like the Brown Recluse.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though activity often peaks in late summer and autumn in outdoor settings.
Description
The Triangulate Cobweb Spider is a common household resident often overlooked due to its small size and preference for dark corners. Its intricate geometric abdominal patterns make it a jewel of the indoor ecosystem, where it provides excellent pest control services.
Key Features
Triangular/zig-zag abdominal markings and a shiny, round abdomen. This species lacks the red hourglass found on Black Widows and has banded legs.
Similar Species
Steatoda grossa (False Black Widow) which is larger and darker, and Latrodectus species (Black Widows) which have a distinct red hourglass and lack the triangular patterns.
Life Cycle
Females produce round, white-to-tan papery egg sacs throughout the year. One female may produce several sacs containing about 30 eggs each. Spiderlings emerge and often stay near the mother for a short time before dispersing.
Ecological Importance
Serves as a primary predator of indoor pests like ants and ticks. They play a significant role in managing urban insect populations without the need for chemical pesticides.
Conservation Status
Not evaluated by the IUCN. It is a very common and widespread species with stable populations globally.
Interesting Facts
The Triangulate Cobweb Spider is recognized as a beneficial predator of the Brown Recluse (Loxosceles reclusa), making it a valuable natural form of pest control in homes where more dangerous spiders are present.
Photography Tips
Focus on the unique geometric pattern on the top of the abdomen. Use a macro lens or phone macro mode with indirect lighting to capture the texture without reflecting off the shiny abdomen.
Identified: 2026-05-21T19:43:46.482539