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Today on Animal Fact Files we’re discussing spiny orb weavers. Spiny orb weavers get their common name from their appearance. Considering there are tens of thousands of spiders alive today, spiny orb weavers aren’t the only pointy spiders in the spider world. In fact, while they’re related to many other spined spiders, there are pointy spiders to which spiny orbweavers seem to have no relation. So, not every spiny spider is a spiny orb weaver, and their scientific classification may change with new information. As it currently stands, there are about 70 species in the spiny orb weaver genus.

Spiny orb weavers are also known as star spiders, thorn spiders, jewel spiders, and crab spiders, though that last one isn’t to be confused with true crab spiders. Spiny orb weavers are found worldwide in tropical and temperate areas, and generally prefer habitats with vegetation in which they can construct their webs. As their common name suggests, these spiders build orb-shaped webs which can reach nearly two feet (61cm) in diameter and hang up to 20 feet (6m) off the ground. They’ll catch flies, moths, beetles, and other insects in their sticky silk. Some spiny orb weavers may even create shared webs with conspecifics. This has both pros and cons. On one hand, the spiders don’t have to work as hard at creating their own web since they can use parts of the webs of their neighbors; on the other hand their eggs may also become more vulnerable to parasites since they’re grouped together and easier to access. Egg sacs can fall victim to flies and other spiders. Adult spiny orb weavers may be afforded some protection from predators due to their spiky protrusions, but they are taken by wasps and other spiders. Jumping spiders are especially diabolical. In one report a jumping spider tickled the outer edges of a spiny orb weaver’s web to attract the spider into striking distance. It did not end well for the spiny orb weaver.

While they aren’t that large, averaging less than half an inch in length, spiny orb weavers are noticeable. They might look dangerous with those conspicuous spines, however, spiny orb weavers are harmless to humans. A bite from a spiny orb weaver may be mildly painful and have a reaction local to the site of the bite, but they don’t do much more than that. What’s more, it’s only the females that sport that large, spiky abdomen. Spiny orb weaver males are much smaller than females, which is pretty common for spiders in general. The males’ spines are far less pronounced which is probably for the best because mating is likely difficult enough with one set of spikes in the web. After mating, the male doesn’t live very long, and the female perishes after laying her eggs. The egg sac she creates can be just as splendid as she is, though. She’ll typically attach it to the underside of a leaf and she’ll use different colored thread such as yellow and green to make sure it sticks. There can be more than 200 eggs inside the sac, and it will typically take them two weeks to hatch and then another two to five weeks before finding their own place in the world.

Also, supposedly these spiders shouldn’t exist. A study found that they have a 19 hour circadian rhythm, which is basically an animal’s internal clock. Research has shown that animals with a natural circadian rhythm that doesn’t match the typical 24 hour day cycle on earth tend to have problems with the health of their offspring. But apparently spiny orb weavers don’t care what science has to say because they just keep doing their thing.

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