Gasteracantha

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. Gasteracantha has a complex taxonomic history, and many questions of species limits and distribution and generic interrelationships remain unanswered. Challenges include the variability within individual Gasteracantha species (e.g., color polymorphism and variable length and shape of spines), a lack of male specimens and descriptions for many species, missing or damaged type specimens, and ambiguous initial descriptions in 18th- and 19th-century scientific literature. The 70 species currently recognized by World Spider Catalog include dozens of synonyms and subspecies, many based on literature well over 100 years old. Gasteracantha is related to several other spiny orb-weaver genera of Africa, Asia, and Australasia: A 2019 study examining three mitochondrial and two nuclear genes found that Gasteracantha is paraphyletic with respect to Macracantha, Actinacantha, and Thelacantha. M. arcuata is allied with G. hasselti and A. globulata, while T. brevispina is closer to G. kuhli and G. diardi. The authors, however, did not propose generic reassignments based on their findings. Micrathena orb-weavers in North and South America also have hardened abdomens with variously shaped spines, but they are not closely related to Gasteracantha within the orb-weaver family.