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Argiope aurantia by Jerry Cates
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The stabilimentum in today's web has been enlarged vertically. What about the central portion? If you look closely and study the web from both days carefully, you will notice that many of the features of yesterday's stabilimentum are present today. However, they appear to have been changed somewhat. Did this mean the spider only added features to the previous web? Or did it dismantle the other and reconstruct a new one with an almost identical stabilimentum? Initially, I guessed the former to be the case. But I got a better idea after a few more days of watching how it works.
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The fun thing about
studying nature is that nothing stays the same. We would have expected this
spider to make changes to its web in the course of the day (she tears the
web down and builds a new one every night), but it is still a bit surprising
to see how many changes occurred in the structure of the new web. The web on
the left was photographed early this morning. The previous web, 24 hours
earlier, is shown below. The spider was on the east-facing surface of the
web when I approached from the east, and immediately scampered off the web
into the vegetation below. Yesterday it was on the west-facing surface and
appeared totally oblivious to my presence, even when I went around to
photograph from the west side. The spider's fright subsided quickly this
morning, and when I accidentally jiggled the web with the camera it
immediately scampered back up, positioning itself in the center of the
hub. Do you think it thought I was a big lunch?
Notice that the spider's legs are not black, but have yellow bands that seem to be placed uniformly along the length of each leg. The spider's carapace is black with a complex yellow marking radiating from its center. This is a juvenile female Argiope aurantia. As it matures, the legs will lose the yellow bands, but the segment near the carapace will be mostly yellow, while the other segments will darken. The carapace will lose its yellow markings, and will become covered with bluish-silver hairs. Today, sitting on the sunlit east-facing surface of the web (yesterday it was on the dark west-facing side, in the shadows) the spider's coloration is much easier to see. Has it grown much in one day? I was first led to think so, based on the size of the body compared to that of the stabilimentum. Notice that its body appears to be almost half as long (41%) as the oval portion of the stabilimentum today, while it was much less than half (38%) in yesterday's photo. Of course, since I didn't measure the stabilimenta, I really could not be sure if the spider is larger, or if the apparent size difference is due to a difference in the dimensions of the stabilimenta from both days. Go back to July 26, 2001 Go to July 28, 2001 * July 29, 2001 * July 30, 2001 * July 31, 2001 |
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