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THE YOUNG NATUKALIST. 



shorter time, depending upon the extent of the variation,. the difference would 

 be quite lost. This absorption of a divergent form, is one of the causes of 

 species remaining permanent. It is only when such divergence is of a char- 

 acter likely to be of service to the species, that it has any chance of being 

 preserved. I am not, however, concerned now with the causes producing 

 alteration of form, but rather with its preservation when produced. Insects 

 like A. caja and A. grossulariala, that vary very much in this country, do 

 not necessarily do so abroad, and though there is not at present any appear- 

 ance of a permanent variety being established of either species, it is quite 

 possible that the causes, whatever they may be, that are producing these extra- 

 ordinary aberrations, will continue to operate until this result is brought about. 



There appears to be some inherent force always operating to perpetuate 

 the existing form, as well as to produce change or variation, and when once 

 a variety has beea established it is easier to retain it than to produce another. 

 Different as are the sexes of many of our butterflies and moths they continue 

 unchanged. Many exotic species differ very much more than ours do, but the 

 same thing obtains with them. Even when two or more forms of the female are 

 found they preserve their special characteristics generation after generation. 

 As in the case of Papilio turnus and glaucus, one batch of eggs will produce 

 males and females differing from each other, or males and two or more forms 

 of the female. We never find species combining the characters of the two. 

 Pieris drassicce, for instance, in which the sexes differ only in markings, 

 never appears with a male showing the markings peculiar to the female, even 

 in a lesser degree. Argynnis pajohia, in which the sexes differ in colour as 

 well as markings, never produces a male with the colour or marking of the 

 female, though like Papilio turnus, it may be quite possible for both sexes 

 and the dimorphic form Valezina to come from one batch of eggs. A male 

 Valezina is said to be in Mr. Bond's rich collection, but a single specimen 

 can only be deemed an accidental aberration, and even if such specimens were 

 frequent they would in no wise be intermediate between one and the other. 

 Mr. Bond's has the markings of the male, but is nearly as dark as the variety. 

 Hermaphrodite specimens have occasionally been taken of Edusa, Semele, 

 and some of the blues. Even these never have the sexual differences in 

 markings mixed. One side will be male and the other female. The variety 

 of Angerona prunaria with dark border is by no means rare, and as I have 

 said, occurs in both sexes. Sometimes the dark border is considerably ex- 

 tended, and nearly covers the wing, a small portion of the centre only, retain- 

 ing any orange scales. I never saw a specimen in which the border was 

 narrow, broken, or suffused with orange. Any such form, might be considered 

 intermediate, but they either do not exist, or are very rare. Black A, 



