Theridiidae, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, is a large family of araneomorph spiders first described by Carl Jakob Sundevall in 1833. This diverse, globally distributed family includes over 3,000 species in 124 genera, and is the most common arthropod found in human dwellings throughout the world. Theridiid spiders are both entelegyne, meaning that the females have a genital plate, and ecribellate, meaning that they spin sticky capture silk instead of woolly silk. They have a comb of serrated bristles (setae) on the tarsus of the fourth leg. The family includes some model organisms for research, including the medically important widow spiders. They are important to studies characterizing their venom and its clinical manifestation, but widow spiders are also used in research on spider silk and sexual biology, including sexual cannibalism. Anelosimus are also model organisms, used for the study of sociality, because it 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 because all permanently social species are highly inbred. The Hawaiian Theridion grallator is used as a model to understand the selective forces and the genetic basis of color polymorphism within species. T. grallator is known as the "happyface" spider, as certain morphs have a pattern resembling a smiley face or a grinning clown face on their yellow body.

They often build tangle space webs, hence the common name, but Theridiidae has a large diversity of spider web forms. Many trap ants and other ground dwelling insects using elastic, sticky silk trap lines leading to the soil surface. Webs remain in place for extended periods and are expanded and repaired, but no regular pattern of web replacement has been observed. The well studied kleptoparasitic members of Argyrodinae (Argyrodes, Faiditus, and Neospintharus) live in the webs of larger spiders and pilfer small prey caught by their host's web. They eat prey killed by the host spider, consume silk from the host web, and sometimes attack and eat the host itself. Theridiid gumfoot-webs consist of frame lines that anchor them to surroundings and of support threads, which possess viscid silk. These can either have a central retreat (Achaearanea-type) or a peripheral retreat (Latrodectus-type). Building gum-foot lines is a unique, stereotyped behaviour, and is likely homologous for Theridiidae and its sister family Nesticidae. Among webs without gumfooted lines, some contain viscid silk (Theridion-type) and some that are sheet-like, which do not contain viscid silk (Coleosoma-type). However, there are many undescribed web forms.

The largest genus is Theridion with over 600 species, but it is not monophyletic. Parasteatoda, previously Achaearanea, is another large genus that includes the North American common house spider. , the World Spider Catalog accepts the following genera: About 35 extinct genera have also been placed in the family. The oldest known stem-group member of the family is Cretotheridion from the Cenomanian aged Burmese amber of Myanmar. - Achaearanea Strand, 1929 – Africa, Asia, Australia, South America, Central America - Achaearyopa Barrion & Litsinger, 1995 – Philippines - Achaeridion Wunderlich, 2008 – Turkey - Allothymoites Ono, 2007 – China, Japan - Ameridion Wunderlich, 1995 – Central America, Caribbean, Mexico, South America - Anatea Berland, 1927 – Australia - Anatolidion Wunderlich, 2008 – Africa, Europe, Turkey - Anelosimus Simon, 1891 – Asia, Africa, North America, South America, Oceania, Central America, Caribbean - Argyrodella Saaristo, 2006 – Seychelles - Argyrodes Simon, 1864 – Africa, Asia, Oceania, North America, South America, Jamaica - Ariamnes Thorell, 1869 – Costa Rica, South America, Asia, Africa, Oceania, Mexico, Cuba - Asagena Sundevall, 1833 – North America, Asia, Europe, Algeria - Asygyna Agnarsson, 2006 – Madagascar - Audifia Keyserling, 1884 – Guinea-Bissau, Congo, Brazil - Bardala Saaristo, 2006 – Seychelles - Borneoridion Deeleman & Wunderlich, 2011 – Indonesia - Brunepisinus Yoshida & Koh, 2011 – Indonesia - Cabello Levi, 1964 – Venezuela - Cameronidion Wunderlich, 2011 – Malaysia - Campanicola Yoshida, 2015 – Asia - Canalidion Wunderlich, 2008 – Russia - Carniella Thaler & Steinberger, 1988 – Europe, Angola, Asia - Cephalobares O. Pickard-Cambridge, 1871 – Sri Lanka, China - Cerocida Simon, 1894 – Brazil, Venezuela, Guyana - Chikunia Yoshida, 2009 – Asia - Chorizopella Lawrence, 1947 – South Africa - Chrosiothes Simon, 1894 – North America, South America, Central America, Caribbean, Asia - Chrysso O. Pickard-Cambridge, 1882 – North America, South America, Central America, Asia, Trinidad, Europe - Coleosoma O. Pickard-Cambridge, 1882 – United States, South America, Seychelles, Asia, New Zealand - Coscinida Simon, 1895 – Asia, Africa - Craspedisia Simon, 1894 – Brazil - Crustulina Menge, 1868 – Ukraine, United States, Africa, Oceania, Asia - Cryptachaea Archer, 1946 – South America, North America, Oceania, Central America, Asia, Trinidad, Belgium - Cyllognatha L. Koch, 1872 – Samoa, Australia, India - Deelemanella Yoshida, 2003 – Indonesia - Dipoena Thorell, 1869 – North America, Oceania, Asia, Central America, South America, Caribbean, Africa, Europe - Dipoenata Wunderlich, 1988 – Panama, South America, Malta - Dipoenura Simon, 1909 – Asia, Sierra Leone - Echinotheridion Levi, 1963 – South America - Emertonella Bryant, 1945 – North America, Asia, Papua New Guinea - Enoplognatha Pavesi, 1880 – Asia, Europe, Australia, Africa, North America, South America - Episinus Walckenaer, 1809 – Asia, South America, Europe, North America, New Zealand, Central America, Africa, Caribbean - Euryopis Menge, 1868 – Asia, North America, South America, Jamaica, Europe, Oceania, Africa, Panama - Eurypoena Wunderlich, 1992 – Canary Is. - Exalbidion Wunderlich, 1995 – Central America, South America, Mexico - Faiditus Keyserling, 1884 – South America, North America, Central America, Caribbean, Asia - Gmogala Keyserling, 1890 – Papua New Guinea, Australia - Grancanaridion Wunderlich, 2011 – Canary Is. - Guaraniella Baert, 1984 – Brazil, Paraguay - Hadrotarsus Thorell, 1881 – Oceania, Belgium, Taiwan - Helvibis Keyserling, 1884 – South America, Panama, Trinidad - Helvidia Thorell, 1890 – Indonesia - Hentziectypus Archer, 1946 – Caribbean, Panama, North America, South America - Heterotheridion Wunderlich, 2008 – Turkey, Russia, China - Hetschkia Keyserling, 1886 – Brazil - Histagonia Simon, 1895 – South Africa - Icona Forster, 1955 – New Zealand - Jamaitidion Wunderlich, 1995 – Jamaica - Janula Strand, 1932 – Asia, South America, Australia, Panama, Trinidad - Keijiella Yoshida, 2016 – Asia - Kochiura Archer, 1950 – Chile, Turkey, Brazil - Landoppo Barrion & Litsinger, 1995 – Philippines - Lasaeola Simon, 1881 – Europe, North America, Panama, South America, Asia - Latrodectus Walckenaer, 1805 – South America, North America, Asia, Europe, Oceania, Africa - Macaridion Wunderlich, 1992 – Europe - Magnopholcomma Wunderlich, 2008 – Australia - Meotipa Simon, 1894 – Asia, Papua New Guinea - Molione Thorell, 1892 – Asia - Moneta O. Pickard-Cambridge, 1871 – Oceania, Asia, Seychelles - Montanidion Wunderlich, 2011 – Malaysia - Nanume Saaristo, 2006 – Seychelles - Neopisinus Marques, Buckup & Rodrigues, 2011 – Panama, Caribbean, South America, North America - Neospintharus Exline, 1950 – North America, Asia, South America, Central America - Neottiura Menge, 1868 – Asia, Europe, Algeria - Nesopholcomma Ono, 2010 – Japan - Nesticodes Archer, 1950 – Asia, New Zealand - Nihonhimea Yoshida, 2016 – Asia, Seychelles, Oceania, Mexico - Nipponidion Yoshida, 2001 – Japan - Nojimaia Yoshida, 2009 – China, Japan - Ohlertidion Wunderlich, 2008 – Greenland, Russia - Okumaella Yoshida, 2009 – Japan - Paidiscura Archer, 1950 – Europe, Algeria, Asia - Parasteatoda Archer, 1946 – Asia, Oceania, Cuba, North America, Argentina, Seychelles - Paratheridula Levi, 1957 – United States, Chile - Pholcomma Thorell, 1869 – Oceania, North America, Asia, South America - Phoroncidia Westwood, 1835 – Asia, Africa, North America, Caribbean, South America, Oceania, Europe, Costa Rica - Phycosoma O. Pickard-Cambridge, 1879 – North America, Asia, Africa, Jamaica, Panama, Brazil, New Zealand - Phylloneta Archer, 1950 – Asia, United States, Spain - Platnickina Koçak & Kemal, 2008 – North America, Asia, Africa - Proboscidula Miller, 1970 – Angola, Rwanda - Propostira Simon, 1894 – India, Sri Lanka - Pycnoepisinus Wunderlich, 2008 – Kenya - Rhomphaea L. Koch, 1872 – Asia, Africa, South America, Oceania, North America, Europe, Central America, Saint Vincent and the Grenadines - Robertus O. Pickard-Cambridge, 1879 – Europe, North America, Asia, Congo - Ruborridion Wunderlich, 2011 – India - Rugathodes Archer, 1950 – Asia, North America - Sardinidion Wunderlich, 1995 – Africa, Europe - Selkirkiella Berland, 1924 – Chile, Argentina - Sesato Saaristo, 2006 – Seychelles - Seycellesa Koçak & Kemal, 2008 – Seychelles - Simitidion Wunderlich, 1992 – Europe, Asia, Canada - Spheropistha Yaginuma, 1957 – Japan, China - Spinembolia Saaristo, 2006 – Seychelles - Spintharus Hentz, 1850 – Pakistan, Caribbean, Mexico, Brazil - Steatoda Sundevall, 1833 – Oceania, North America, Asia, Europe, South America, Africa - Stemmops O. Pickard-Cambridge, 1894 – South America, North America, Central America, Caribbean, Asia - Stoda Saaristo, 2006 – Seychelles - Styposis Simon, 1894 – United States, South America, Central America, Congo - Takayus Yoshida, 2001 – Asia - Tamanidion Wunderlich, 2011 – Malaysia - Tekellina Levi, 1957 – United States, Brazil, Asia - Theonoe Simon, 1881 – Tanzania, Europe, North America - Theridion Walckenaer, 1805 – Asia, North America, Central America, Europe, South America, Africa, Oceania, Caribbean - Theridula Emerton, 1882 – Spain, Africa, North America, Central America, Asia, South America - Thwaitesia O. Pickard-Cambridge, 1881 – Panama, South America, Africa, Asia, Oceania, Trinidad - Thymoites Keyserling, 1884 – South America, Central America, Asia, North America, Caribbean, Greenland, Tanzania - Tidarren Chamberlin & Ivie, 1934 – Africa, Yemen, North America, Argentina, Costa Rica - Tomoxena Simon, 1895 – Indonesia, India - Wamba O. Pickard-Cambridge, 1896 – North America, South America, Panama - Wirada Keyserling, 1886 – Mexico, South America - Yaginumena Yoshida, 2002 – Asia - Yoroa Baert, 1984 – Papua New Guinea, Australia - Yunohamella Yoshida, 2007 – Asia, Europe - Zercidium Benoit, 1977 – St. Helena

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