What is "velvet spider"

n. any spider, of the family ''Eresidae'', that build unkempt webs

The velvet spiders (family Eresidae) are a small group (about 100 species in 9 genera) of almost totally Old World spiders (exception: a few species are known from Brazil). The characteristics of this family of spiders are that they are entelegyne (have a genital plate in the female), eight-eyed araneomorph spiders that build unkempt webs. They are cribellate (use woolly silk). Some species are nearly eusocial, lacking only a specialized caste system and a queen. They cooperate in brood rearing, unlike almost most other spiders except for some African agelenid spiders in the genus Agelena and a few others.

Female velvet spiders exhibit a remarkable type 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.

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