Gasteracantha (known as spiny-backed orb-weavers, spiny orb-weavers, or spiny spiders) is a genus of orb-weaver spiders first named by Carl Jakob Sundevall in 1833. The females of most species are brightly colored with six prominent spines on their broad, hardened, shell-like abdomens. The name Gasteracantha is derived from the Greek gaster (γαστήρ), meaning “belly, abdomen”, and akantha (άκανθα), meaning “thorn, spine”. Spiny-backed orb-weavers are sometimes colloquially called “crab spiders” because of their shape, but they are not closely related to the true crab spiders. Other colloquial names for certain species include thorn spider, star spider, kite spider, or jewel spider.
Members of the genus exhibit strong sexual dimorphism. Males are several times smaller than females, and they lack prominent spines or bright colors.
Gasteracantha is distributed worldwide in tropical and subtropical climates. The genus is most diverse in tropical Asia, from India through Indonesia. One species, G. cancriformis, occurs in the Americas. Gasteracantha species are related to spine-bearing orb-weavers in several other genera (see Taxonomy and Systematics).
Orb-weavers’ bites are generally harmless to humans.