Cobweb Spider, Red-and-black Cobweb Spider
Tidarren sisyphoides
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Small, globular abdomen with a distinct reddish-orange cephalothorax and anterior abdomen shading into a dark, glossy black posterior abdomen. Noticeable sexual dimorphism is present in this family, though this specimen exhibits typical theridiid proportions with slender legs radiating from a compact body.
Size Estimate
Body length approximately 4-6 mm with a leg span of roughly 15-20 mm. This appears to be an adult or sub-adult specimen.
Coloration & Markings
Striking bicolored appearance featuring a vibrant reddish-orange forebody and front portion of the abdomen, transitioning sharply into a solid, glossy jet-black rear abdomen.
Web Type
Irregular tangle web (cobweb) constructed in protected areas, corners, under eaves, or close to the ground.
Eye Arrangement
Eight eyes arranged in two rows of four, typical of the family Theridiidae, with small, oval shapes clustered on the anterior portion of the cephalothorax.
Leg Characteristics
Slender, dark brown to black legs of moderate length, lacking heavy spination, radiating evenly in a typical sprawling cobweb spider posture.
Venom & Safety Information
Venom Information
Neurotoxic venom typical of cobweb spiders, primarily used to subdue small invertebrate prey. Very low potency regarding humans.
Medical Significance
Harmless to humans. While technically capable of biting if heavily pressured against skin, bites are extremely rare, non-medically significant, and result in minimal local irritation.
Safety Recommendations
No special safety measures needed as they are harmless. If found indoors, they can be gently relocated outside using a container and a piece of paper.
Habitat & Behavior
Habitat & Range
Found throughout warmer regions, often inhabiting gardens, under rocks, debris, and around human habitations in crevices and dark corners.
Behavior & Temperament
Timid and non-aggressive. Relies on its web for catching prey and will drop to the ground or retreat when disturbed.
Diet & Prey
Generalist insectivore feeding on small crawling and flying insects such as ants, flies, and beetles trapped in its sticky web.
Seasonal Activity
Most active during spring and summer months when insect prey is abundant, retreating to sheltered crevices during colder winter periods.
Description
This striking little spider immediately catches the eye with its vivid bicolored contrast of fiery red and glossy black. Belonging to the family Theridiidae, it leads a quiet life constructing messy webs in sheltered spots, silently helping to keep local insect populations in check.
Key Features
Distinctive bicolored body featuring a reddish-orange cephalothorax and anterior abdomen contrasting sharply with a solid glossy black posterior abdomen.
Similar Species
Some small male widow spiders (Latrodectus species) or other cobweb spiders in the family Theridiidae, distinguished by specific ventral markings and abdominal shapes.
Life Cycle
Females produce spherical silk egg sacs containing dozens of eggs, hanging them within the web retreat. Spiderlings disperse via ballooning after hatching and go through multiple molts to reach maturity.
Ecological Importance
Acts as an effective natural predator of small arthropods, contributing to the balance of local micro-ecosystems and pest regulation.
Conservation Status
Not evaluated by the IUCN, but populations are stable, widespread, and common within their natural ranges.
Interesting Facts
Certain males in the genus Tidarren are known for amputating one of their palps before maturity to increase agility, leaving them with a unique asymmetrical appearance.
Photography Tips
Use macro lenses with natural diffused lighting or an external ring flash to capture the fine contrast between the red and black regions without causing the spider to drop from view.
Identified: 2026-10-08T22:44:46.172592