This reveal for Sign Challenge #1 is long overdue. Here’s the challenge photo again:
Commenter Daniel Heald correct guessed it was a spider egg sac. Here’s another angle:
When I took the photos, I assumed it was a cocoon. I was curious to see what moth would emerge, so I took it home with me.
After looking through Tracks & Sign of Insects and Other Invertebrates, I realized it was actually an egg sac for a Spinybacked spider (Gasteracantha cancriformis). In fact, I had seen many of those spiders in the area. The egg sac’s yellow silk, dark longitudinal line, and placement on the underside of a leaf all point to this species.
In Spiders of the Carolinas, L. L. Gaddy notes that in over twenty years of fieldwork he’s not seen the egg sac or male of this species. Perhaps I’m just lucky, but I suspect I’m more of a leaf flipper than Gaddy. The egg sacs are placed on the undersides of leaves, which is where I’m always checking for caterpillars.
I was curious to see the spider eggs, so I peeled back a few layers of the silk and found the spiderlings had already hatched. Turns out they stay in the egg sac for weeks before emerging.
I had hoped to see the spiderlings grow, but they all died after a few weeks.
This thread-legged bug appears to be hanging in mid-air, but in fact it has delicately balanced itself on a spider web. Its beak holds a small spider that it must have just plucked from the center of the web.
Some thread-legged specialize in spiders, and I wonder if this might be one of them. Some are even known to lure the spider by plucking at the web like captured prey might.
When I first spotted this female Nephila clavipes, she was positioned rather low in her web. Her background was cluttered and shaded. I prodded her a few times, and as I’d hoped, she retreated to a higher position in her web where I thought I might be able to get a more pleasing background.
Unexpectedly, her quick movements drew the attention of a male that was also hanging out in her vicinity. I’ve read that males prefer to mate when the female is preoccupied with a meal (so they’re less likely to become a meal themselves). Perhaps he mistook her quick retreat as movement toward prey. At any rate, he wasted no time approaching her and getting into a mating position.
I kept snapping away the whole time. This was the only keeper, which I’m pretty happy with. I took awhile to settle on the right settings that yielded a pleasing background with adequate depth of field. Then I just shot away and hoped some would yield the right plane of focus. I didn’t quite nail it, but it looks pretty good at this resolution.
It was complete luck that this photo shows pretty clearly the tips of the male’s palps, where he stores sperm prior to mating. The tip of one can be seen pointing rearwards. The tip of the other is inserted into the female’s reproductive opening, the epigyne.
Finally, is it just me, or does it seem like the females of this species might just be putting on some sexy lingerie for the males? Just look at the pattern on the underside of her abdomen!
Canon EOS 60D
Canon EF100 Macro lens
Canon MT-24EX flash
Shutter priority AE, 1/160 sec, ISO 800, f/6.3
Exposure compensation -1 1/3
Flash exposure compensation -1
I’ve never quite been happy with any of the photos I’ve taken of this species, Nephila clavipes. This photo is no exception. I do like that it captures the gold color of the web, and that at least a few of the leg tufts are in focus.
It’s a shame the spider lost a leg somewhere along the way. The missing leg distracts me every time I look at her.
These spiders really are quite large. This one measured around 30mm, 70mm if you throw in the legs.
See if you can spot the little fly that’s perched on her abdomen.
Argiope spiders are easy to recognize. They sit head down in the center of their webs with their legs paired up. They don’t even bother to hide themselves during the day. They are among a relatively small number of orb weavers that add a decoration to their web, called a stabilimentum.
The form of the stabilimentum may change as the spider grows. Young spiders like this one may create a dense circular pattern as shown here. Older spiders are more likely to create sparser designs in various shapes.
According to the World Spider Catalog, there are five species of Argiope in Costa Rica: argentata, aurantia, blanda, savignyi and trifasciata. Some I’m familiar with and can eliminate, but that still leaves a few this could be. It does however match a photo here of A. savignyi.
When I recently considered upgrading my camera body to the Canon 60D, I convinced myself it would be more versatile because of the flip-out LCD screen combined with live view. I’m happy to say I wasn’t just lying to myself in order to justify the upgrade. This spider was just one subject from the trip that I would have otherwise had to pass up. Here, I held the camera well above my head with the screen pointed down for focusing.
One of my books (below) has a picture of a very similar looking spider identified as a spiny flag spider, Alpaida cornuta, also from Costa Rica. I wasn’t able to find anything online though using either the common name or the scientific name. The World Spider Catalog doesn’t seem to recognize that name at all, but I saw two species there from Costa Rica, A. bicornuta and A. championi. Perhaps this is one of those.
Here’s a similar looking unidentified Alpaida from Ecuador, so I think the genus is probably correct.
This spider was on an exposed ridge overlooking the sanctuary. She appears to have caught a nice sized wasp.
This species often creates an X-shaped design (stabilimentum) in their web, and you can just see a hint of one extending to the lower right.
The common name Silver Argiope is consistent with the scientific name (argentata = silvery). Even the common name in Portuguese, Aranha-de-prata, translates as Silver Spider. It is indeed silvery.