36 



THE YOUNG NATURALIST. 



characteristics of the male, and on the other 

 of the female. Such specimens are generally 

 called Hermaphrodites, but it is quite an 

 erroneous application of the term to use it 

 in such cases. Monstrosities are very rare, 

 probably becanse insects having defects of 

 this kind are seldom able to complete their 

 changes so as to appear in the perfect state. 

 Specimens of this class have little or no 

 scientific value. Mr. Mosley in his " Illus- 

 trations of Varieties of British Lepidoptera" 

 makes a remark in speaking oiLycance Alexis 

 worth quoting. He is speaking of specimens, 

 with wings of the male colour on one side, 

 and of the female on the other, and says, 

 " Most of the old specimens have the male 

 colour on the right side, while those of recent 

 years have it on the left." If this really be 

 so it is very curious. 



Aberrations. 

 Aberrations are those specimens which 

 depart from the wing markings of the 

 type in a marked degree, but of which 

 only single specimens occur. They are 

 interesting as showing the extent to which 

 variation is possible, and the direction 

 which it will probably take when circum- 

 stances call it forth. Some species are 

 excessively prone to produce aberrations, 

 and it is an interesting fact that those insects 

 having the greatest range of variation, and 

 producing the largest number of extreme 

 forms, are the least able to establish a local 

 race or true variety. To take as an illustra- 

 tion an insect well known to beginners, 

 Chelonia caja may well be selected. Its 

 brilliant colours and very distinct markings 

 make it easy to notice any change, and in 

 the most ordinary examples there may be 

 seen very considerable differences. The 

 number, width, and direction of the cream- 

 coloured lines on the fore wings, and the 

 size and shape of the dark spots on the hind 

 wings, show considerable modification in 

 ordinary examples. In extreme forms the 

 white lines on the fore wings increase in 



width until the darker markings entirely 

 disappear, or they become narrower and 

 fewer until the limit of variation is reached 

 in the opposite direction and the wing is all 

 dark. So with the hind wings : the spots 

 increase in size till they coalesce and form 

 a band, or cover the entire wing, or they 

 diminish till there is scarcely a trace of 

 them left. Then other changes are found : 

 the red on the hind wing appears on the 

 fore wing also ; the yellow of the fringe 

 spreads over all the hind wing ; and other 

 even more abnormal modifications occur, 

 until one is lost in wonder at their extent 

 and beauty. There can be no doubt that 

 it is the extreme tendency of this and simi- 

 lar species to vary that has prevented the 

 formation by them of any distinct form. 

 An insect occasionally varying slightly in 

 one direction is far more likely to produce 

 a permanent variety than one like caja that 

 is always varying in all directions. Besides, 

 there does not appear to be any advantage 

 to the insect itself in any one of these forms 

 over any other. 



I speak of the tendency of an insect to 

 vary in certain directions, but it may be 

 that some of the examples we see rather 

 show a reversion to an older form than the 

 first steps towards the formation of a new 

 one. Though I speak of caja as an insect 

 that is not able to establish any distinct 

 modification, it must not be understood that 

 this has always been so. No one could look 

 at even a limited collection of allied species 

 such as occur in Europe without seeing that 

 they must all have descended from some 

 earlier form that bore certain characteristics 

 yet common to all its descendants, some 

 of which are still found in species now con- 

 sidered to be of different genera, while the 

 greater the number of species we examine 

 the more are we confirmed in this view. 

 The question of reversion then must not be 

 lost sight of, as it has an important bearing 

 on the phenomena we have to consider, and 



