THE .SPIDER 



111 



spiders make webs of the silk that they spin and that many 

 ground spiders line their nests with silk. Silk is, however, used 

 for many other purposes, and it would be difficult to say 

 which is the principal use. The mass of eggs that the female 

 lays is always covered by a 



L^ 



cocoon of silk. The silky 

 threads may serve also to 

 suspend the spider while it 

 drops from a tree, or they 

 may, by their friction with 

 the air, serve to suspend cer- 

 tain spiders in aerial migra- 

 tions.^ This latter use is es- 

 pecially noteworth}^ A small 

 spider, when desirous of tak- 

 ing flight, chmbs up some 

 high object, such as a fence 

 post, elevates the spinnerets, 

 and spins loose silk into the 

 air (Fig. 118). After enough of it has been thus formed, the 

 spider lets go, and is suppoi'ted bj^ the currents in the air 

 while it is wafted great distances. Thus Darwin, on his 

 voyage in the Beagle, saw cobwebs bearing up spiders floating 

 in the air over his vessel more than sixty miles from shore. 



1 The ballooning hal^it of spiders has been noticed since early times, but 

 it was formerly misinterpreted. Thus Pliny speaks of wool being rained. 

 The poet Spenser wrote : — 



" More subtle web Arachne cannot spin; 

 Nor the fine nets, which oft we woven see, 

 Of scorched dew, do not in tli' ayre more lightly flee." 

 Thompson writes: — 



" How still the breeze! save what the filmy threads 

 Of dew evaporate brushes from the plain." 



Fig. 112. — Web of Hyptiotes in a 

 bush, one quarter of the real di- 

 ameter. 



