SOME OF THE "LOWER ORDERS" 201 



from the immediate neighbourhood in which they 

 emerged from the pupal stage. In either case some 

 means of informing the males of the presence of females 

 is an imperative necessity for the continuation of the 

 race. This is provided by means of a subtle odour 

 exhaled by the females which, though imperceptible to 

 human nostrils, must possess an extraordinarily pene- 

 trating power. Weismann gives an instance of this in 

 the case of the nocturnal Eyed Hawk-moth (Smerinthus 

 ocellatus). He placed some females, without any special 

 intention, in a covered vessel near an open window. 

 " The very next morning several males had gathered, 

 and were sitting on the window-sill, or on the wall of the 

 room close to the vessel, and by continuing the experiment 

 I caught, in the course of nine nights, no fewer than 

 forty-two males of this species, which I had never believed 

 to be so numerous in the gardens of the town. . . ." To 

 this power of exhaling odours we may attribute the wing- 

 less condition of many Moths, for otherwise the loss of 

 flight would have brought about extinction long before 

 any perceptible reduction in the wings had taken place. 

 The odour which such prisoners emit seems to possess 

 an irresistible attractiveness, and this fact is commonly 

 taken advantage of by entomologists. The Common 

 Vapourer Moth {Orgyia antiqua) affords a good illus- 

 tration of this. The female is wingless, and little more 

 than a pouch for eggs, but in certain seasons it is very 

 abundant, even in the midst of London. That experienced 

 entomologist Prof. Selwyn Image, in a letter to my friend 

 Mr. John Cooke, remarks, on this theme, that the Cater- 

 pillars may be seen crawling by hundreds in and around 

 the squares, while the males may be seen flying up and 

 down New Oxford Street or Tottenham Court Road. If 



