ARTHROPOD A 



213 



SPIDERS (araneida) are of widespread distribution and, although 

 comprising some 14,000 species, are conveniently divided according to 

 their habits into two types, the relatively sedentary " web-spinners " 

 and the more active " wanderers " which hunt their prey ; all, how- 

 ever, sjiin silk, either as a web, or for snaring or tying up their victims, 

 for protection of their cocoons or for making bridges for travelling. In 

 both types on the cephalothorax there are G or more usually 8 simple 

 eyes arranged in two or three rows (Fig. 212) ; these have received a 

 c«j:>'' ^'^rable amount of study. ^ The arrangement of these ocelli varies 

 remarkably (Figs. 213 to 216). Among the web-spinners the ocelli are 

 rudimentary and their effective range is short. The common house 



Figs. 213 to 216. — The Arrangement of the Ocelli in Different 

 Species of Spiders. 



Fig. 213. — The ocelli of tlu* comtnon 

 house spider, Te'jcu'irio doinestica. 



Fic;. 214. — The ocelli of the common garden 

 spider, Araueus dldilcmatus. 



Y\Q. 21.5. — The ocelli of the wolf FiG. 216. — The ocelli of the jumping spider, 



spider, Li/ro.sd lujricoht. Salticus scenicu.s. 



1 For details, see Hentschel (1899), Widmann (1908), Petrunkevitch (1911), Scheuring 

 (1914), Versluys and Demoll (1923), Savory (1928), Homanu (1928-53), Millot (1949). 



