92 ZOOLOGY 



glands, and their bite is often fatal to insects, and even to 

 small birds and mammals. But most spiders cannot spread 

 the chelicene sufficiently to make a bite in the human skin, 

 and even the largest forms seem to inflict but a slight 

 wound, scarcely ever greater than that of a mosquito. 

 The stories of the severe effects of the bite of the Taran- 

 tula, one of the Lycosidse, are entirely fabulous. 



Spiders show a marked sexual dimorphism. Particularly 

 among the orb-weavers the males are much smaller than 

 the females of the same species, but the legs of the male 

 are relatively the longer and stronger. The male is usually 

 shorter lived than the female, for the latter has often to 

 watch the egg-cocoons, or carry them about with her until 

 the young hatch out. The male also builds less perfect 

 webs than the female. The relation existing between 

 mated pairs is often peculiar. The male is frequently 

 killed and eaten by the female; but if the male can over- 

 come the female, she may fall his victim. Among wander- 

 ing spiders there is often a selection by the female from 

 among several rivals, which engage in severe battles with 

 each other. 



Allies of the spider must be briefly mentioned. The 

 spider belongs to the class Arachnoidea, 1 characterized as 

 follows : Air-breathing, wingless arthropods, whose head 

 and thorax are usually united to form a cephalothorax, 

 which bears two pairs of jaws and four pairs of legs ; the ab- 

 domen, which is not always separated from the cephalo- 

 thorax, possesses no legs. The principal subdivisions of 

 the Arachnoidea are as follows : - 



The Arthrogastra, 2 including the scorpions and their 

 allies, are characterized by the fact that the abdomen is 



j, spider ; eUos, form. - dpdpov, joint ; yarnf/p, abdomen. 



