The spinybacked orbweaver (Gasteracantha cancriformis) is a small species of spider found throughout South America, Central America, the Caribbean islands, and the southern part of North America. They can reside in a variety of habitats, but their main home is in woodlands and dense brush. They are mainly solitary, but will sometimes coexist with other colonial orbweaver spiders.
G. cancriformis is notable for its striking appearance. The head and thorax are small and , while the thorax is quite large and lined with six sharp spines. The coloration can vary throughout the spider's distribution; generally the head and thorax are black, while the abdomen can be white, black, orange, yellow, or even blue, and the spines can be red or black. Females tend to be between 5–9 mm (0.20–0.35 in) long, while males are much smaller at only 2 to 3 mm (0.1 in) long.
As an orbweaver, spinybacked orbweavers build large webs to catch their prey-- mainly small insects. Every evening, a female builds a new web and a male hangs by a single thread close by. The following morning, after consuming any insects she has caught, the female will either take down or eat the web so that a new one can be constructed the following evening. Depending on the size of her prey, she may either paralyze it with a mild venom or wrap it in webbing before consumption. There are few known predators of adult spinybacked orbweavers, due to their small size and prickly defense, but the eggs are known to be parasitized by wasps.
Spiny orbweavers only live for one year, and only mate once during that period. In the spring, males court females first by drumming on her web. If she does not become aggressive, he approaches and allows her to strap him down with silk. Following copulation, the female lays an egg sac with 100 to 260 eggs on the underside of a nearby leaf, and then dies. The male typically dies several days later; it is unknown whether he mates with other females during this period. Incubation takes 2-5 weeks, and the young mature quickly over the summer.
Conservation status: The IUCN has not evaluated the spinybacked orbweaver. However, the species has a large, widespread population, and is highly adaptable to living in urban areas, and so is generally considered stable.
Photos
Scott Nelson
Judy Gallagher
Kimberlie Sasan
