THE YOUNG NATUEALIST. 



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Leaving out questions of structure, sexual differences are not confined to 

 butterflies. In most of Bombyces they are very marked. In Noctuse they 

 are generally slight, but the hind wings of the female are darker than those of 

 the male in very many instances. In the Geometrse many of the females 

 differ in a very striking manner from the other sex. Who for instance would 

 suppose males of Epione vespertaria to be the same species as the females at 

 first sight. 



It is not necessary to go out of England for illustrations of well marked 

 and permanent varieties not sexual. Anger ona prunaria, in which the sexes 

 differ considerably in colour, has produced a very distinct variety, common to 

 both sexes, in which a broad dark border appears round all the wings. 

 Amphidasis letularia has a well known black variety f Boubledayaria) also 

 common to both sexes. Such species as Xylophasia rurea, var. combusta, 

 Hepialus velleda, var. carnus, Folia chi, var olivacea, and others are too well 

 known to need comment. Some of the class of varieties of which these may 

 serve as illustrations may be more or less local, or confined to particular dis- 

 tricts, others occur anywhere with the type, but they are all tolerably common, 

 and distinct enough to have been thought different species. 



There are other species much subject to variation in which no distinct 

 form has as yet been produced. The common Tiger, Arctia caja, and the 

 Gooseberry Moth, Abraxas grossulariata are special favourites with variety 

 breeders in this country, and are excessively variable. Every change that 

 can be rung on black, brown, red, yellow, and white has been produced in A, 

 caja. Some are all black or brown, some all white ; yellow displaces red in 

 the hind wing ; red displaces white in the fore wings. In Grossulariata, the 

 colours are fewer ; black, white, and yellow only appearing. Yet the different 

 appearances it assumes are marvellous. The narrow band of yellow that runs 

 across the wing, spreads over the entire surface, and deepens to orange. The 

 black spots disappear, leaving the specimen perfectly immaculate, they become 

 semi-transparent, they form bands or streaks, or they spread over the entire 

 wing. Yet in neither of these species has any permanent variety been pro- 

 duced, unless the nearly black form of Grossulariata known as Varleyata, 

 Porritt, be considered such. 



When a form occurs, presenting a marked departure from the type, it must 

 in a state of nature, almost certainly pair, if it pair at all, with an ordinary 

 specimen. The progeny of such a pair may reasonably be expected to par- 

 take of the characters of both parents, some differing not so much from the 

 type as the one, nor yet so closely resembling it as does the other. These, 

 pairing again with the ordinary form, should produce offspring that at this 

 second generation are still less divergent than the first, and after a longer or 



