Thursday, July 21, 2011

The traumatic lives of the Kalimna Golden Orb Weavers

The four Golden Orb Weavers (Nephila edulis) at Kalimna Park were introduced in the June 7 blog. Nicknamed for ease of remembering, K-large was the largest. K-top was up high and also very large, and K-medium was at the same height as K-large, but not as large. Unlike the other three, half-sized K-Littley's web didn't intersect with the others. She was just a juvenile. Six weeks later, and a lot has happened. This is the abbreviated version, with only a few of the hundreds of photos I have now taken. It's been exciting, and it's been sad. [Click on pictures for larger images.]

K-Large had a very large abdomen, indicating that she was ready to lay eggs, or was eating really well! Her little male was in attendance for a week or so. You can see the engorged ends of his pedipalps (aka palps, the small leg-like things on the front). That boxing glove look means that he is a male looking for sex. He has already ejaculated the sperm and collected it in those engorged palps. That means he has got that done and can now concentrate on surviving the mating game. The males of lots of species survive. Nephila don't. If he manages to mate with her, she will store his sperm until she makes her egg sac and releases her eggs. They will be fertilised on the way out.

A few days later, the other three were still in their places, but I couldn't see K-Large until I looked up. She was on a branch at the top of her web, looking larger than ever.

The next day, she was skinny and completing her egg sac.

A day later, and she was adding some bark blobs to disguise it.

And there she stayed, for weeks. She made a small web to hang on but never again a large web to trap insects. K-Top was also large and had a male in attendance. She duly made her egg sac. Like K-Large, she added bark, or bark-like fake blobs, to her egg sac and made a small web nearby to rest on.

Then there was a storm, a really windy, cold rainy night. The next day, I couldn't see two of my three large Nephila. K-Littley was still in her place, on a ragged web, but still there. K-Large was with her sac, but K-Top's egg sac was deserted. I looked all over and eventually found K-Medium and K-Top together right over on the side of K-Medium's web, a good three metres from K-Top's egg sac. They were covered in rain drops, just hanging from the web. Skinny K-Top on high, and medium sized K-Medium below. But a tap on the web induced a small movement in K-Medium. At least she was still alive. I hoped there might be some chance of a recovery.

The next day, and they were both looking like normal Nephila on the web together. But it didn't last for long. A few days later, K-Medium was dying on her web. As her hydraulic system stopped pumping fluid into her legs, they were retracting.

The next day, after another night of heavy rain, she was dead on the ground. She had not made an egg sac, and now, never will.

Another night of rain, and I couldn't find the two adults anywhere. I haven't seen them again. K-Littley was covered in rain drops, but still fine.

And so it has been ever since. The other adult Golden Orb Weavers I was watching have all gone. Only K-Littley is left. But there are three fine egg sacs to check every day. Welcome's egg sac in the garden, along with K-Large and K-Top's up in Kalimna Park.

There's a lot of other spiders around, and another arachnophile giving me some great photos to post. Watch this space!

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