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 six 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 effects 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!
are they poisionios???????
All spiders are venomous, but I’ve never heard of anyone suffering from ill effects of this spider’s bite. Its fangs aren’t too large and its venom is not very potent. This is not considered a dangerous spider.
I would NOT spray these spiders. They kill many gnats,flies and mosquitoes and are beneficial. In fact, they are one of the best ways to control mosquitoes which carry diseases such as West Nile virus. The Star Spiders like to build orb webs in trees or bushes and are not harmful to people. But they collectively they can kill millions of mosquitoes over time. They are one of the best natural biological control agents for mosquito control. Actually we should be mass rearing these spiders and releasing them to control mosquitoes as diseases like West Nile virus can kill people such that these spiders are actually saving people’s lives!
Visit Spiders and Flies at byteland.org/spidersandflies/index.html where I have posted photos of Gasteracantha cancriformis, aka the Star Spider or Crab-like Spiny Orb Weaver
Thanks, Dr. TAL.
I have no plans whatsoever to spray these spiders; I like having them around. I remove their webs when they’re blocking a walkway, but other than that, all are welcome here. Thanks for the link to your site; interesting stuff.
just finally moved into our new home in st. augustine, fl about 10 days ago and found at least 50 org weaver spiders in my screened in pool area. Are they poisonous? How should i remove them?
Hi, Rebecca.
All spiders are venomous but very few can do more than annoy. Many, in fact, have fangs too small even to pierce human skin. Some of the larger orb weavers can bite, though. I’d recommend a broom to sweep them outside. Pesticides around a pool are bad news. Do you know what species of orb weaver you have?
–Ben
I am curious why you say pesticides around the pool are bad news. What do you mean by that?
Well, we swim in a pool. We absorb chemicals through our skin. I’m not sure that the chlorine in the pool breaks down pesticides in anything like a safe manner. But it’s not something I’ve studied or researched.
Is there a reason to want to swim in a pool that’s full of pesticides? Or some research out there that shows that pesticides break down harmlessly in a typical swimming pool environment?
I found it! It is a golden orb-weaving spiders (Nephila edulis) http://museumvictoria.com.au/about/mv-blog/categories/melbourne-museum/ look half way down the page! Thanks S
Hi, Susie.
Glad you were able to find your spider! Based on your research, I could guess that the one in my yard is our common N. American golden silk orb-weaver, Nephila clavipes. Only thing is, I haven’t seen any on this property, and they’re so conspicuous I doubt I’d have overlooked them. Their webs are gigantic, and they themselves are about the biggest spider most people ever see…
Hi,
I have this exact same egg mass and hatching in my East West Palm. I found it yesterday and today when I looked again the spiderlets were coming out. The thing is – I am in Brisbane Australia!!
Did you confirm what sort of spider they are?? The tree is close to our house – so I wouldn’t want 100′s of poisonous spiders coming inside!
Please let me know – this is genuine – I have the pictures on my phone.
Thank you Susie
By the way it was hanging from a palm flower branch – attached with fine white threads – we thought it was a silk worn cocoon but after I saw all the spiderlets this morning obviously we’re wrong !! Thanks again Susie