Theridiidae
A diverse family of spiders common in human dwellings worldwide.
They are both entelegyne and ecribellate, with a comb of serrated bristles on the tarsus of the fourth leg.
- common_names
- tangle-web spiders, cobweb spiders, comb-footed spiders
- key_characteristics
- entelegyne, ecribellate, comb of serrated bristles on fourth leg tarsus
- oldest_fossil
- Cretotheridion from Cenomanian Burmese amber
Lore & Background
Theridiidae spiders build a variety of webs, often tangle space webs, hence the common name. Many trap ants and other ground-dwelling insects using elastic, sticky silk trap lines leading to the soil surface. Their webs remain in place for extended periods and are expanded and repaired, but no regular pattern of web replacement has been observed. Gumfoot-webs consist of frame lines and support threads with viscid silk, and can have either a central retreat (Achaearanea-type) or a peripheral retreat (Latrodectus-type). Building gum-foot lines is a unique, stereotyped behavior likely homologous for Theridiidae and its sister family Nesticidae. Some webs lack gumfooted lines, including those with viscid silk (Theridion-type) and sheet-like webs without viscid silk (Coleosoma-type).
Reader's Guide
Theridiidae includes several model organisms for research. The medically important widow spiders are used in studies of venom and its clinical manifestation, as well as research on spider silk and sexual biology, including sexual cannibalism. Anelosimus species serve as models for the study of sociality, because sociality has evolved frequently within the genus, allowing comparative studies across species, and because it contains species varying from solitary to permanently social. These spiders are also a promising model for the study of inbreeding, as all permanently social species are highly inbred. The Hawaiian Theridion grallator, known as the 'happyface' spider, is used to understand selective forces and the genetic basis of color polymorphism within species. Kleptoparasitic members of Argyrodinae live in the webs of larger spiders, pilfering small prey, consuming silk, and sometimes attacking the host. The family's diversity in web forms and behaviors makes it significant for evolutionary and ecological studies.
Did You Know?
- Theridiidae is the most common arthropod group found in human dwellings throughout the world.
- The family includes the medically important widow spiders, used in venom and silk research.
- The Hawaiian Theridion grallator is known as the 'happyface' spider due to a pattern resembling a smiley face on its yellow body.
- Kleptoparasitic members of Argyrodinae live in the webs of larger spiders and pilfer prey or consume silk.
Frequently Asked Questions
Who is Theridiidae?
Theridiidae is a large, diverse spider family best known for building irregular, tangled webs rather than the classic orb designs. They are found in virtually every human-inhabited region on Earth and are among the most frequently encountered spiders in homes and gardens.
What are Theridiidae's common names?
Fans and field guides typically call them tangle-web spiders, cobweb spiders, or comb-footed spiders, the last name referencing the distinctive bristle structure on their legs.
What are Theridiidae's key physical traits?
Every member of the family is both entelegyne and ecribellate, and they all carry a comb of serrated bristles on the tarsus of the fourth leg. That bristle comb is the diagnostic feature that separates them from other spider families.
How far back does the Theridiidae fossil record go?
The oldest known representative is Cretotheridion, a specimen preserved in Cenomanian-age Burmese amber, pushing the family's documented history back roughly 99 million years.
Why is Theridiidae important to arachnid fans?
Their ubiquity in human dwellings worldwide makes them the family most people actually see up close, and their long fossil lineage plus the unique comb-foot morphology make them a favorite subject for both fieldwork and evolutionary discussion.
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