Welcome to You Ask Andy

Robert Cole, age 12, of Holley, New York, for his question:

Does a spider ever get caught in her own web?

A stupid spider could get caught in her own web. But she would never grow old enough to have spiderlings. This means that the stupid mistake is not passed on to another generation. Hundreds of different spiders spin webs. Each species repeats the special design inherited from her ancestors. She knows how it works to catch her food. She also knows how to avoid getting caught in her own web.

Spiders belong in the Class Arichnida. Some 50,000 species have been identified, though not all of them spin silken webs. Some are trapeze artists who spin silken tightropes to swing themselves from bough to bough. Some weave funnel shaped traps and others build nets of tangled threads. Many arachnids also spin cozy cocoons for their eggs.

The champion web weaver is the orb spider. She is the species most likely to make us wonder why she doesn't get caught in her own booby trap. She is a master builder and it is a treat to get up early to watch her weave her beautiful round web. The job begins at dawn and takes about an hour. If this little arachnid were human sized, she could build a log cabin in one hour.

Her raw material is liquid silk, manufactured in a gland at the tail end of her big, fat abdomen. The tacky stuff is piped through her spinning organ, which is a group of spinnerets like tiny faucets. The liquid silk cannot be squirted out through the spinnerets. The spider presses her abdomen against a solid surface to squeeze out the first drop. She sticks this to a leaf or twig, and walks away. As she goes, she uses a leg to draw out more silk and it dries to a gossamer thread in the air.

A spider can manufacture threads of different widths and strengths. The orb spider uses her sturdiest silken rope to construct the supporting cross threads. She walks around on this scaffold, testing to see that the end of the ropes are firmly fixed to twigs and leaves and that enough of them meet in the center. Then she spirals around on the gridwork, paying out finer thread as she walks. Every few paces she stops to add a tiny gob of tacky goo. She gives a little twang to spread the goo along the spiralling thread.

When the gauzy net is completed, all the circling threads are covered with sticky glue. But there is none in the lines across the web. Flying insects do not know this    but the spider does. She waits in a secret corner until a fly zooms into her trap. She watches as his struggles tangle him tighter in the sticky threads, then comes forth to claim her dinner. She trips safely across the web because the little smartie places each of her eight feet on the non sticky cross lines.

By the time the spider reaches her struggling prey, he is securely wound up in silken bonds. Usually she bites him to inject a paralyzing poison. After dinner, she trips back on the non sticky threads to her corner. One or two victims tear her web to shreds. Almost always she has to build another one at dawn the next day.

 

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