Spiny orb-weavers is a common name for Gasteracantha, a genus of spiders. They are also commonly called spiny-backed orb-weavers, due to the prominent spines on their abdomen (compare genus Isoxya). These spiders can reach sizes of up to 3 cm (1.2 in) in diameter (measured from spike to spike). Although their abdomen is shaped like a crab shell with spikes, it is not to be confused with a crab spider.
Often brightly colored, spiny orb-weavers have a broad, hard abdomen that can be white, orange, or yellow with red markings. The female shell is ringed by six red or orange spines, whereas the smaller male lacks the spiny projections and instead has four to five stubby dark projections.Yellow spiny back orb weaver spider. Photographed in New Orleans, Louisiana, USA
Orb-weavers' bites are generally harmless to humans.Gasteracantha geminata