Signature Spider Egg Sacs

Description:

When an Argiope luzona spider creates an egg sac, she usually positions it about 18 to 20 inches from her web and she strings it up with a few strong strands of silk. Having observed these egg sacs many times, I can say, with some confidence that the incubation period is usually from 6 to 10 days (at least that is what I have observed in the area where I live) and then the hatchlings emerge in great numbers (according to Wikipedia, anything from 400 to 1,400 hatchlings). These minuscule spiders congregate near the empty egg sac and they appear to form a three dimensional “cloud” of very fine spider silk. I don’t know for sure, but I think they feed out a silk thread as they move around and that is what forms the “cloud”. However, I have been struggling with a problem. I could understand that once the “cloud” had formed, the hatchlings could move around on it and it seemed to be attached to the egg sac and to any other nearby branches or twigs. So, that was O.K., but when the first two or three hatchlings walked out of the sac, what were they walking on? There was no “cloud” yet and they were not near enough to be stepping onto part of the mother’s web. So, what was going on that I was missing. I could not see any structure, in place, ready to support a bunch of little spiders rushing out of the egg sac. Well, I lived with that question in my understanding (of my favourite spiders) for a few months, but I now have the answer. In recent weeks, I have been taking some photos of spider webs, especially early in the morning. As we all know, spider webs are usually pretty much invisible, but when the morning sunshine strikes a web at just the correct angle, it sparkles like a diamond and just for a moment, the amazing work of the spider can be seen in great detail. So, I started thinking about the hatchlings again… what if there was something beside the egg sac that I could not see? I couldn’t find an egg sac that was in a good position for the morning sunshine. So, I had to look for another way of seeing if there was anything there. I am not a great photographer and I don’t have a fancy camera, but I fiddled around with the controls and took dozens of bad photos of egg sacs which showed absolutely nothing. Then, suddenly, I got a faint hint of some silk threads. So, I fiddled some more and I got the first of my photos shown above. There was, indeed, a fine criss-cross silk structure right beside the egg sac. I moved on to another egg sac that I knew, and without changing my camera settings, got another similar result, my second picture above. I did it one more time, my third picture, and I knew that I had the answer to my problem. The female spiders had built a kind of scaffolding, using very fine silk and, although I had no chance of seeing these structures with the naked eye, the camera (plus a little brightness and contrast adjustments on my laptop) revealed them.

Habitat:

All of these Argiope luzona (Signature Spider) Egg Sacs were spotted in our backyard.

Notes:

Argiope luzona egg sacs have a light coloured side and a dark coloured side. When photographing these egg sacs, I prefer to get pictures of both sides so that I can select the best side for my spotting photos. Obviously, the dark coloured side does not stand out very well against a dark background and vice versa. In my first three photos, I chose the light coloured side for all three of them. I would have liked to have the light side for the last photo also, but as you can see. the egg sac was close up against a fence. So, a view of the dark side was all that I could get. The last photo was taken seven days ago and is only included here to show the “cloud” of hatchlings.