Diagnostic characters
- Legs many times the body length, thin and flexible with a visible flex at the tarsus
- Cylindrical, elongate abdomen in Pholcus; globular in Physocyclus
- Pale grey or tan, often translucent
- Whirls or bounces rapidly in the web when disturbed
- Female carries a loose bundle of eggs in her chelicerae rather than in a silk sac
Habitat and seasonality
Basements, cellars, garages, crawlspaces, closets, under eaves and decks, and in caves and rock overhangs.
Present year-round in heated and sheltered structures; effectively aseasonal indoors.
Medical significance
None documented. Chelicerae are short but functional, and there is no evidence of any clinically relevant venom effect in humans.
The venom myth
The claim that daddy long-legs have the most potent venom of any spider but fangs too short to penetrate human skin is false in both halves. No toxicological study has ever demonstrated unusually potent pholcid venom, and pholcid chelicerae are entirely capable of piercing human skin, producing at most a brief mild sensation.
The confusion is compounded by the term daddy long-legs being applied to three unrelated animals in different regions: pholcid spiders, harvestmen in the order Opiliones, and crane flies in the order Diptera. Harvestmen have no venom glands and no silk glands at all.
Predation on other spiders
Pholcus phalangioides is a specialist invader of other spiders' webs. It plucks the resident's web to mimic prey vibration, then swathes the approaching occupant in silk from a safe distance using its long legs. Documented prey includes Latrodectus and Tegenaria, which makes the family a genuine, if modest, biological control agent in structures.
Management
Cellar spider webs accumulate rapidly because the spiders abandon soiled tangles and build adjacent to them rather than repairing. Mechanical removal with a vacuum is fully effective and residual insecticide application is not justified. Reducing basement humidity and insect entry addresses the underlying prey supply.
Families most often confused with Pholcidae
| Family | How to separate it |
|---|---|
| Opiliones (harvestmen) | Harvestmen are not spiders: one body segment, two eyes, no silk, no venom glands |
| Theridiidae | Cobweb weavers are stockier with much shorter legs and a globose abdomen |
| Tipulidae (crane flies) | Crane flies are insects with wings and six legs |
Profiled species in this family
| Species | Scientific name | Medical significance |
|---|---|---|
| Cellar Spider | Pholcus phalangioides | none |
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.