84 



ZOOLOGY 



A small spider, when desirous of taking flight, climbs up 

 some high object, such as a fence post, elevates the spin- 

 nerets, and spins loose silk into the air (Fig. 81). After 

 enough of it has been thus formed, the spider lets go, and 

 is supported by 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. 



The method of spinning 

 deserves careful attention. 

 The spinning-organs consist 

 of a set of glands lying in the 

 hinder part of the abdomen, 

 and opening to the exterior 

 through a number - often 

 several hundred --of spin- 

 ning "spools." These spools 

 are the modified mouths of 

 glands, and are grouped 

 upon and between tubercles 

 called spinnerets. The 

 secretions of the glands, as 

 they are poured out into 

 the air, fuse together and 



harden into a thread. The thickness of the thread is 

 determined by the number of glands secreting together. 



" More subtle web Arachne cannot spin ; 

 Nor the fine nets, which oft we woven see, 

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



Thompson writes : 



" How still the breeze ! save what the filmy threads 

 Of dew evaporate brushes from the plain." 



