v] TRAP-SNARES AND BALLOONS 37 



evaporate." The phenomenon in question is the 

 occasional appearance of vast numbers of silken 

 flakes which fill the air, and which in some recorded 

 instances extend over many square miles and to a 

 height of several hundred feet. Our observations 

 will have given a clue to its origin which is entirely 

 attributable to spiders, and in large measure to their 

 ballooning habit, though no doubt reinforced by a 

 large quantity of silk spun for other purposes and 

 caught up into the air by the breeze. For a vivid 

 account of such a shower the reader is referred 

 to Letter LXV of White's Natural History of 

 Selborne, and Darwin in his Naturalist's Voyage 

 (Chap. VIII) records a case of the "gossamer spider" 

 descending in multitudes on the "Beagle' when 

 sixty miles from land. 



In the ballooning habit we have the probable 

 explanation of the wide distribution of certain 

 species of spiders which seem at first exceedingly 

 ill adapted for covering large distances. The Hunts- 

 man Spider, Heteropoda venatorius, is practically 

 cosmopolitan in tropical and sub-tropical regions and 

 the usual view has been that ships have conveyed it 

 from port to port. McCook, however, gives several 

 reasons for believing that the trade winds have much 

 more to do with the matter, and this may well be the 

 case, though both agencies have doubtless been at 

 work. 



