rilOTECTIVE MIMICRY. 247 



that iatroduces some difficulties. It would be supposed that 

 mimetic females pairing with non-mimetic males would pro- 

 duce a progeny of a mixed kind — not so perfectly mimetic as 

 the female parent; in this way the effectiveness of the mimicrj 

 would tend at once to disappear, and finally would disappear. 



When the Eyed Hawk moth produces a hybrid with the 

 Poplar Hawk moth, the offspring imites the characters of both 

 parents. 



As to the results of breeding from dissimilar parents a few 

 other instances may be mentioned. Near Manchester the 

 common Pepper-and-Salt moth (Bistoii betularia) shows a 

 well-marked melanic variety, which is gradually getting more 

 abundant. This instance of an apparent connection between 

 local conditions and a colour variety may be added to those 

 mentioned in Chapter II. A male of the melanic variety was 

 crossed with a female of the common form. The offspring 

 were intermediate in coloration, and showed very beautiful 

 markings. The same insect was experimented with under the 

 same conditions (i.i'. a melanic male with a normal female), and 

 produced a different result : the offspring consisted of eleven 

 individuals, eight males and three females ; six of these were 

 melanic and live normal. It is clear, therefore, that the colour 

 varieties do Jiot coincide with the sex. 



Another supposition — also based upon facts — is that the 

 progeny would be divided, one portion having a preponderance 

 of characters derived from the male parent, the other portion 

 aii'reeing more closely with the female. This, again, would 

 tend in the course of tune to destroy the mimetic resemblance, 

 unless the female offspring were alwai/s like the female 

 parent. 



But there is another difficulty to be faced. 



If the females escape destruction by virtue of their likeness 



