AEAGHNIDA. 143 



The head bears from six to eight simple eyes ; the mandibles 

 are hooked, and carry the duct of a poison-gland; and the 

 maxillary palpi are not developed into nipping-claws. The 

 spiders are all predaceous and rapacious animals, and many of 



Fig. 59. — Araneida. Thmndion riparian (female). 



them possess the power of constructing webs, either for the 

 capture of their prey, or simply for lining their habitations. 

 For the production of the web, spiders are furnished with 

 special glands, situated at the extremity of the abdomen. The 

 secretion of these glands is a viscid fluid, which hardens rapid- 

 ly on exposure to air, and which is cast into its proper thread- 

 like shape by passing through what are called the "spin- 

 nerets." These are Uttle conical or cylindrical organs placed 

 at the end of the abdomen, and perforated by a number of ex- 

 tremely minute tubes, through which the secretion of the 

 glands has to pass before reaching the air. Many spiders, 

 however, do not construct any web, unless it be for their own 

 habitations, but simply hunt their prey for themselves. 



The spiders are oviparous, and their young pass through 

 no metamorphosis, but they cast their skin, or " moult," re- 

 peatedly before they attain the size of the adult. 



