SHIP- AND WIND-BORNE COLONISTS 309 



Thursday Island. I have seen them too at ahiiost every point 

 between Java Head and Cocos-Keeling. They are merely 

 flying over the sea instead of flying over the land, and they 

 are certainly not in any way to be regarded as unfortunate 

 storm-driven exiles. Butterflies that are members of strongly 

 flying families do the same ; they fly away from the land in a 

 perfectly irresponsible way. Moths come nightly to a ship's 

 lights when she is lying twenty miles from the shore. 



I do not for one moment suggest that any of these insects 

 are voluntary colonists, but I am quite sure that it is wrong 

 to regard all insects that are met with Avhen far from land as 

 being wind-borne strays, swept from their homes by gales. 

 Many of them start the journey of their own free will — an 

 aimless and irresponsible journey it is true, but not by any 

 means invariably an involuntary one. When once at sea, 

 without shelter or resting-place, they do become true waifs, 

 and then the wind disposes of them as it will. 



The case of these dragonflies, which come in such numbers 

 and are so conspicuous, is certainly only an easily recognised 

 example of what is happening perpetually to an infinity of 

 other creatures, and it makes real the most important fact in 

 Nature's colonisina: — that the number of her failures must be 

 enormous. 



In the first place, either both sexes must arrive at the 

 same time, or the one be ready waiting ashore for the other ; 

 or else a pregnant female must come prepared to undertake 

 the responsibilities of maternity in a new land. Vast numbers of 

 waifs must arrive in vain — stray solitary individuals, unmated 

 females, or members of one sex only. Then every creature 

 that has, after a perilous journey, the good fortune to eflect a 

 landing on the atoll, still has its fate undecided, for no suitable 

 environment may be at hand for it and its progeny. The 

 dragonflies have no fresh water, and therefore cannot pro- 

 pagate their kind. Countless other waifs, when they had 

 made a successful landing, all ready to carry on the reproduction 

 of their species, must have sought in vain for any plant which 

 would serve as the food for their larvae, or for any nidus which 



