Florida spider: Gasteracantha cancriformis

One of the most familiar spiders to Florida residents is the spiny orb weaver, Gasteracantha cancriformis. You’ll see people flailing their arms wildly after running into their webs all the time. This actually happened a lot at our old house, because these little guys make fairly large webs, and they loved to decorate our front porch back at the old house. They were so abundant in the fall that I’m tempted to call it our halloween spider; they might as well have been our trick-or-treat decorations.

This fall, though, at the new place, they’re a bit more scarce, although that might change soon, as you’ll discover after reading this post. Just this morning I ran into one web while I was trimming the ficus hedge our next-door neighbor so thoughtfully installed between our two properties:

As you can see, it’s black and white and red all over. That is, the dorsal portion of the abdomen is white with black spots, and there are eight red spines projecting out rather threateningly. Local folks (myself included) often call this a “crab spider,” even though it’s really not related to the crab spider group (Thomisidae).

Gasteracantha is an Old World pantropical genus; G. cancriformis is the only member of the group to occur in the Americas, where it is widely distributed, ranging from the southern states to Argentina.

While all spiders are venomous, the bite of this species, despite its fearsome (if diminutive) appearance, is not known to cause serious [i.e., lethal] effects in humans.

The reason I’m posting about it today, after years of neglect, is that I finally ran across an egg sac and dozens upon dozens of spiderlets. As I said, I was trimming the ficus hedge (our neighbor’s yard crew trims her side of the hedge, but our side, even though I’d rather burn the hedge down, is up to me to tend), and this little bit of garden work brought me into contact both with the adult web (which extended down from our Royal Poinciana tree into the hedge I was working on) and, I later discovered, the yellow egg sac.

Here’s a shot of the egg sac:

It’s about an inch long (25 mm) and slightly less than that wide (15 mm). You can see all the spiderlets crawling all over it; there must be a couple hundred of them! I took a brief video of it, if you’re interested:

I’m not entirely sure that this is a “crab spider” hatch-out, but I haven’t seen many other orb weavers around here. The folks at bugguide.net haven’t nailed down an ID for me yet, but they do seem to think that this might not be G. cancriformis after all.

If it is (and even if it isn’t), the etymology of the spiny orb weaver is refreshingly uncomplicated: Gaster is Greek for belly, of course, while acantha is Greek for horn; cancer is the Latin version of crab, and form is, well, our latinate word form. So this is the horn-bellied (or abdomened) crab-shaped animal. Hooray!