THE ENTOMOLOGIST. 23S 



when the abdomen was pressed, a very disagreeable odour 

 was exhaled ; but he had never seen any fluid ejected. 



Dr. Sharp read the following propositions, in contravention 

 of the theory of mimetic resemblances advanced and so in- 

 geniously advocated by Messrs. Wallace and Bales : — 



1st. That natural selection was a power of differentiation, 

 and, although it was quite possible that a differentiating 

 power might work so as to produce resemblances, it was at 

 first sight improbable that it should do so ; and more evi- 

 dence was required of the truth of a paradox than of a 

 truism. 



2nd. It must be shown that animals possessing the so- 

 called mimetic resemblances occurred far more frecpiently in 

 company with one another than away from one another. But 

 if this were shown, a single case of such resemblance between 

 animals living in different localities would throw doubt on the 

 theory, by suggesting that there was probably some more 

 comprehensive law which would account for all those resem- 

 blances. 



3rd. It must be shown that the cause of the rarity of the 

 Leptalis was one acting on the insect entirely or chiefly 

 while it was in the perfect state : this had not been done, 

 and it was improbable that it could be ; for the most critical 

 periods in the life of Lepidoptera, as regarded their enemies, 

 were the larval and pupal states. 



4th. It must be shown that the enemy (whatever it might 

 be) which attacked the Leptalis sought its prey principally 

 by the sense of sight ; but this suggested another impro- 

 bability. If the Heliconia, which the Leptalis resembled, 

 was protected by its nasty odour, surely the bird or other 

 enemy of the Leptalis must be very foolish to let it escape 

 when it smelt nice, because it looked like the Heliconia. 

 The purpose of protection would have been better accom- 

 plished by the Leptalis mimicking the Heliconia in that- 

 point by which the Heliconia was protected. 



5th. A forcible objection to the mimicry theory (as already 

 pointed out by Mr. Westwood) was the rarity of the mimicking 

 species. The theory involved the hypothesis that there was 

 a time when the Leptalis differed in pattern from the Heli- 

 conia; was the Heliconia then commoner than now, or as 

 rare ? If commoner, it was curious that, when not protected, 



