Velvet spiders (family Eresidae) are a small group (about 100

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

in 9

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

) of spiders almost entirely limited to the

Old World The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...

, with the exception of one species known from Brazil. In Europe, some are commonly called the ladybird spiders.

Description

This family can sometimes be confused with the

jumping spider Jumping spiders are a group of spiders that constitute the family (biology), family Salticidae. , this family contained over 600 species description, described genus, genera and over 6,000 described species, making it the largest family of spide ...

s, or those in the Palpimanidae family. These spiders are usually black or brown in colour, though they can also have brighter colours as pictured. As their common name implies they can look quite smooth and velvety. They usually live in silken tubes under objects, or underground, but the genus '' Stegodyphus'' builds silken nests.

Identification

They can be distinguished from most species except the Penestomidae by their semi-rectangular

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

and clypeal hood. They can be distinguished from Penestomidae by the eye arrangement, straight anterior eye row and strongly recurved posterior eye row, with the median eyes close together. Adonea eye group

Social behavior

Some species are nearly

eusocial Eusociality ( Greek 'good' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations wit ...

, lacking only a specialized caste system and a queen. They cooperate in brood rearing, unlike most other spiders except for some spitting spiders, African agelenid spiders in the genus '' Agelena, Monocentropus balfouri'' and a few others. Female velvet spiders exhibit a remarkable type of maternal care unique among arachnids. Upon the birth of her brood, the mother spider liquefies her internal organs and regurgitates this material as food. Once her capability to liquefy her insides is exhausted, the young sense this and consume the mother. Rachel Nuwer, ''Scientific American'', October 2015. Spiders of the genus ''Stegodyphus'' genus, such as '' Stegodyphus sarasinorum'' in India, are known for their elaborate and robust nests and their colony integrity.

Genera

The genus ''Penestomus'' was previously placed in Eresidae as the subfamily Penestominae, but was elevated to its own family, Penestomidae, in 2010. , the

World Spider Catalog The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of ...

accepts the following genera: *'' Adonea'' Simon, 1873 — Portugal, Algeria, Palestine *'' Dorceus'' C. L. Koch, 1846 — Africa, Asia *'' Dresserus'' Simon, 1876 — Africa *'' Eresus'' Walckenaer, 1805 — Africa, Asia, Europe *'' Gandanameno'' Lehtinen, 1967 — Namibia, South Africa, Malawi *'' Loureedia'' Miller, Griswold, Scharff, Řezáč, Szűts & Marhabaie, 2012 — Africa, Asia *'' Paradonea'' Lawrence, 1968 — Namibia, Botswana, South Africa *'' Seothyra'' Purcell, 1903 — Africa *'' Stegodyphus'' Simon, 1873 — Africa, Asia, Brazil

References

* Lehtinen, P.T. (1967): Classification of the cribellate spiders and some allied families, with notes on the evolution of the suborder Araneomorpha. ''Ann. Zool. Fenn.'' 4: 199–468. * Dippenaar-Schoeman, A.S. (1989): The African species of the subfamily Penestominae (Araneae: Eresidae): with description of two new species. ''Phytophylactica'' 21: 131–134.

External links