TRACHEA TA 415 



complete form in the mature female, and appears after the 

 ninth or last moult. 



The testis in the male consists of two caeca, placed ven- 

 trally in the anterior part of the abdomen ; each passes into a vas 

 deferens, and the two vasa deferentia unite together in a small 

 vesicle which opens to the exterior just behind the level of the 

 pulmonary sacs. In Tegenaria guyonii the semen is deposited 

 on a web constructed for the purpose, and taken up by the 

 palpal organs and by them introduced into the spermatheca of 

 the female, an operation not unattended by danger, as the 

 female, when hungry, has been known to seize and devour 

 the small male. The number of eggs laid varies from 

 above one thousand (Argiope eophinaria) to two {Oonops 

 pulcher) ; they are generally deposited in cocoons. The Lyco- 

 sidae carry their cocoons attached to the abdomen of the 

 mother, and when the young are hatched they are borne on 

 her back till the first moult. Theridion carries the cocoon 

 between the base of the legs, and if it be lost searches about 

 diligently till it is found. 



The Araneida are divided into two sub-orders : 



1. Teteapneumones, with four lung sacs, and as a rule 



four spinnerets. 



2. DiPNEUMONES, with two lung sacs and six spinnerets. 



Sub-order 1. Teteapneumones. 



These are large hairy spiders which do not weave webs, 

 but burrow in the earth, lining their tubular tunnels with a 

 thick web. They sit at the entrance of these holes waiting for 

 their prey, which, in the case of the gigantic South American 

 Mygale avicularia, often takes the form of small birds. Other 

 members of this sub-order are Cteniza and Nemesia, the trap- 

 door spiders, found in Southern Europe ; these genera close 

 the entrance of their tubular home with a lid or trap-door. 

 Both these genera have two pairs of spinnerets, of which the 

 posterior pair are very long and bend up over the abdomen. 

 Atypus, the only genus of Tetrapneumones found in Britain, 

 has six spinnerets. 



The endosternite, which was well developed in Zimulus and 



