Tuesday, February 3, 2009

Spider female guarding egg sac.
Female spiders are usually larger than the male as the physical demands and accompanying energy requirements to produce webs and broods, are far greater. The male is smaller because once mature, his only function is to mate. Where males are similar in size to the females, they are generally more slender, with longer legs. In some cases the male can be one thousandth of the weight of the female. In other cases, the male and female are so different that they may even appear to be different species where males of certain species mimic wasps or ants.
Once mature, the male abandons all usual activities such as web construction and prey capture and transforms into a sexual attractions. Spider courtship is hazardous for the male spiders. It requires planning ahead, a good strategy, knowing the whims of your future mate and in some cases, the ability to perform long, arduous routines to please her - sometimes at the risk of being eaten by her. Once he has located a mate, the male spider dare not make a false move as it would mean certain death so the female is approached cautiously.
As the eggs develop in the female, her abdomen enlarges. After a period varying from 1 week to several months after mating, the female lays her eggs in the safety of darkness. About 1000 eggs can be laid in 8-10 minutes. Some spiders only produce a few eggs while few species can produce up to 9000 eggs and only about 2% survive to maturity. Spider eggs are roughly spherical, and about 1 mm in diameter; they are laid in a compact mass and covered to a greater or lesser extent with silk, forming a sac. The eggs are variously colored, pale brown, pale yellow, pink, even bright green. Underfed females lay less eggs but the size depends upon the species. Some spiders produce more than one sac, but there is a tendency for fewer eggs in the later sacs. Most species however spin much more substantial cocoons or egg-sacs to hold the eggs safe. This is particularly necessary to species where the mother dies before the eggs hatch. But some wolf spiders however live to see their young hatch.
The tiny hairless and blind creature must wait a few days to moult into a more advanced stage, the larva, which has rudimentary eyes and a few hairs but lacks poison and the ability to spin silk. Both of these stages are unable to feed and they subsist off the yolk within them. After a short period, the larva moults into a nymph or spiderling which resembles the adult in general form. At this stage, some cannibalism may take place within the sac, and those spiderlings which are weak becomes meal for others.
Yuwaraj Gurjar.


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