12 SPIDERS [CH. 



All spiders spin, but it is by no means all spiders 

 that make snares for the purpose of catching prey. 

 The fundamental purpose of the spinning organs 

 seems to be to connect the spider with its point 

 of departure. The jumping spiders (Aitidae) make 

 no snare, but this "drag-line" as it has been called 

 comes in very useful when stalking prey on the 

 vertical surface of a wall, when a miscalculation at 

 the moment of pouncing upon it would entail a 

 considerable fall were it not for such an anchorage. 

 It can hardly be doubted though of course it is 

 incapable of proof that all the more complicated 

 spinning operations originated in this universal spider 

 habit, but all known spiders have learnt to apply 

 their power of making silk to other purposes. If 

 they do not make snares they at least spin "cocoons" 

 for the protection of their eggs, and if they have a 

 definite home from which they emerge to seek food, 

 such a retreat is always more or less lined with silk. 

 It is clear that a spider cocoon is quite different from 

 that of an insect ; it encloses the eggs and is 

 manufactured by the mother, whereas among the 

 insects the larva makes the cocoon for the protection 

 of the pupa or chrysalis into which it is about to turn. 

 However far from exhaustive the foregoing study 

 of spider structure may be it Avill suffice for our 

 purposes, at least for the present, and we may 

 proceed at once to an investigation of one of the 



