358 



ARACHNIDA ARANEAE 



Working upon a water plant some distance below the surface, it 

 forms a silken dome of closely-woven threads, which it next 

 proceeds to fill with air. To do this the spider rises in the 

 water, raises its abdomen above the surface, and jerks it down 

 again quickly, so as to carry with it a bubble of air which it 

 helps to retain with its hind legs. AVith this it swims back 

 to its tent, into which it allows the imprisoned air-globules to 

 escape. By degrees the dome or bell is filled, and the creature has 

 a dry and snug retreat beneath the water. In this it passes the 

 winter in a torpid condition. The young of this species appear 

 to be fond of utilising the empty shells of water-snails, which 

 they float by filling them with air, and thus save themselves the 

 trouble of nest-construction. 



Cocoon. — The last important spinning operation which remains 

 to be described is the building of the so-called cocoon. This must 

 be distinguished from the cocoon of insects, which is a protective 



covering of silk within 

 which the larva assumes 

 the pupa form. In the 

 case of the Spider, the 

 term is applied to the 

 structure which serves to 

 protect and conceal the eggs. 

 It is often of considerable 

 complexity, and is highly 

 characteristic of the parti- 

 cular species which con- 

 structs it. 



All egg-bags are com- 

 menced in very much the 

 same way. A small sheet 

 of silk is woven, and against 

 this, sometimes upon the 

 upper and sometimes on the 

 under surface, the eggs are 

 deposited, and then covered in with a second silken layer. The 

 compact silk-covered ball of eggs is then, in many eases, enclosed 

 in a small compartment which the spider builds with infinite care 

 and unfailing uniformity, after the pattern peculiar to its kind. 

 A considerable number of the Orb-weavers are content with a. 



Fig. 196. — Egg-cocoons. A, Epeira diademata, 

 nat. size. B, Theridion pollens x 4, attached 

 to a leaf. C, Agroeca irimnea, nat. size, 

 attached to a weed, and not yet coated with 

 mud. D, Ero furcata x 4, attached to a log. 



