Diagnostic characters
- Cribellum, a silk-spinning plate anterior to the spinnerets, and a calamistrum comb on leg IV
- Silk appears woolly, bluish, and non-sticky to the touch
- Tufts of hair on the tibia of leg I in Uloborus, giving a feathered appearance
- Rests stretched flat in a horizontal web
- Hyptiotes builds a triangle web of only four radii and holds it under tension
Habitat and seasonality
Eaves, porch ceilings, sheds, greenhouses, conifer branches, and shaded understory.
Adults present through the warm season; sheltered indoor populations persist longer.
Medical significance
None. The family possesses no venom glands.
Venom loss
The absence of venom glands in Uloboridae is a derived loss, not an ancestral condition, and it is compensated for by extreme wrapping behavior. An uloborid may apply well over a hundred metres of silk to a single prey item, wrapping so tightly that the insect is physically crushed before digestive enzymes are introduced.
Triangle web
Hyptiotes builds a partial orb consisting of a triangular sector with four radii, then holds the structure taut between an anchor line and its own body. When prey contacts the web the spider releases the tension, collapsing the silk around the insect. It is one of the few documented cases of external power amplification by an animal.
Families most often confused with Uloboridae
| Family | How to separate it |
|---|---|
| Araneidae | True orb weavers use viscid glue droplets and possess venom glands |
| Theridiidae | Cobweb weavers build tangles rather than orbs and lack a cribellum |
References
- [1]World Spider Catalog, version 26 - Natural History Museum Bern. Accessed 2026-06-14.
- [2]Spiders of North America: An Identification Manual, 2nd ed. - American Arachnological Society. Accessed 2026-06-14.
- [3]Common Spiders of North America - University of California Press. Accessed 2026-06-14.