Re: orb weavers and their bodies

Spiders first bite their prey, injecting venom to kill it, and then 
liquefy as much of the prey as possible while the prey is still outside 
the spider.  They do this by the secretion of powerful enzymes.  Some 
spiders have teeth on their chelicerae (mouthparts) that allow them to 
further this process by the maceration (crushing) of the prey.   Others 
have to suck out the liquefied internal parts of the prey through the 
holes produced by the fangs. Once inside the spider, the liquid is further 
digested and distributed.  Orb-weaving spiders eat their webs because the 
silk protein represents a high cost in energy to the spider.   The 
digestion of the silk returns some of the energy lost in silk production.

Reference:  Foelix, R. F. Biology of Spiders, 2nd ed. 1996.  Oxford Univ. 
Press, New York.