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Spider Egg Sac

12-10-12 spider egg sac3 IMG_6616As a result of many years of evolution, spiders have developed the use of different silks produced by seven glands for various functions (ballooning, webs, wrapping prey, dragline, egg sac, etc.).  The tubuliform gland is responsible for the large diameter silk fibers used in the construction of egg cases.  Unlike other silk glands, which synthesize protein throughout a spider’s lifetime, the tubuliform gland synthesizes silk for only a short time in a spider’s life, just before eggs are laid.  This silk is synthesized only by female spiders, and is the stiffest type of silk, which makes it a very protective covering for eggs. The pictured overwintering spider eggs had three layers of protection:  bark (the photo is of the underside of a piece of loose bark), an outer silk cocoon covering the egg sac and the egg sac itself – a tough layer of silk covering the eggs. (Reluctantly I opened the sac for the sake of an educational photograph, and did my best to re-wrap the eggs.)

3 responses

  1. Kathie Fiveash

    What is the true size of the eggs?

    December 10, 2012 at 8:48 pm

    • The egg sac was about 1/4″ in diameter — the eggs were each roughly 1/32″.

      December 10, 2012 at 10:07 pm

  2. nangalland

    Who would have thought spider eggs could look so tenderly, luminously beautiful? Another stunning photo! Thank you!

    December 11, 2012 at 11:33 am

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