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 much smaller cephalothorax. The abdomen is notably shiny and rounded, characteristic of the 'False Widow' group. The surface is smooth with fine, sparse hairs.
Size Estimate
Body length 3–6 mm (1/8 to 1/4 inch). Leg span is typically 12-15 mm. This specimen appears to be an adult female.
Coloration & Markings
The cephalothorax is brownish-orange to dark brown. The abdomen is brownish-black with a distinctive pattern of off-white or yellowish triangles or zig-zags along the dorsal midline. Legs are pale yellowish-brown with faint darker bands at the joints.
Web Type
Tangle web or cobweb; a messy, three-dimensional silk structure typically built in corners, under furniture, or near floorboards.
Eye Arrangement
Eight eyes arranged in two rows, typical of Theridiids; they appear as small glistening beads but are difficult to see without macro magnification.
Leg Characteristics
Relatively thin and tapering; the front legs are longer than the others. They lack conspicuous spines but have fine hairs (setae).
Venom & Safety Information
Venom Information
Contains latrodectus-like toxins but in much lower concentrations and potency than true Black Widows. Attacks the nervous system of prey but is generally weak against humans.
Medical Significance
Low medical significance. Bites are extremely rare and typically result only in localized redness, minor swelling, or a slight stinging sensation similar to a bee sting.
Safety Recommendations
Generally harmless. If relocation is desired, use a glass and a piece of paper to move the spider outdoors. Wear gloves when cleaning dark, dusty corners to avoid accidental nips.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Inhabits dark, low-traffic areas of homes (basements, crawlspaces) and outdoor structures like sheds or woodpiles.
Behavior & Temperament
Shy and sedentary. They spend most of their lives tucked away in their webs. They are not aggressive and will usually retreat or play dead (thanatosis) if disturbed.
Diet & Prey
Generalist predator of small arthropods, including ants, flies, ticks, and even other spiders such as Brown Recluses or larger House Spiders.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though most visible in late summer and autumn during peak mating.
Description
The Triangulate Cobweb Spider is a common, unobtrusive house guest often mistaken for its more dangerous relatives. Known for its geometric abdominal markings, it is a master of domestic pest control, quietly vibrating its web to snag wandering insects and even medically significant spiders.
Key Features
Triangular patterning on a dark abdomen, small bulbous body, and preference for dark indoor corners.
Similar Species
Steatoda grossa (False Black Widow), which is larger and lacks the distinct triangles; Latrodectus mactans (Black Widow), which has a red hourglass on the underside.
Life Cycle
Females produce round, white to tan papery egg sacs, visible in the web. One female can produce several sacs per year. Lifespan is approximately 1–2 years.
Ecological Importance
Significant domestic predator that controls populations of ants, mosquitoes, and indoor pests without the use of chemical pesticides.
Conservation Status
Not evaluated; widespread and extremely common in human-occupied areas.
Interesting Facts
Study has shown these spiders can prey on Brown Recluse spiders, making them beneficial 'security guards' in homes where recluses are present.
Photography Tips
Focus on the dorsal (top) of the abdomen to capture the triangle pattern. Use a macro lens or 'Portrait' mode with side-lighting to highlight the glossy texture and silk lines.
Identified: 2026-07-19T07:34:42.390850