White Butterjiies of Britain. 225 



marked by most persons to be those which are white; and 

 all these, it may be inferred, are usually looked upon as of the 

 same species, differing in nothing, except perhaps in the size; 

 the latter being erroneously ascribed to difference of age, ac- 

 cording to the analogy of birds, quadrupeds, and fishes. But 

 the fact is, that there are a considerable number of species of 

 our white butterflies, as well as several genera ; and probably 

 more varieties even of these than have yet been ascertained or 

 described. To these I shall now endeavour to direct the 

 reader's attention. It may be of use, however to make the 

 previous remark, that butterflies do not, like the larger ani- 

 mals, increase in size as they grow older: for every in- 

 dividual, from the moment it becomes a butterfly, continues 

 invariably of the same size from its birth till its death. But- 

 terflies, indeed, seldom live longer than a few days, or, at 

 most, a few weeks, and during this time they eat little except 

 a sip of honey : and since this is so, it would be absurd to 

 expect that they could increase in size. It must not, however, 

 be understood from this that the same species will always 

 measure or weigh precisely the same ; for, though this will 

 hold as a general rule, there are many exceptions, arising 

 from the accidents the caterpillar may have suffered from 

 which an individual butterfly originated. It is only during 

 the caterpillar state that the insect eats voraciously and grows 

 in proportion ; and if it is, during this stage of its existence, 

 , thrown upon short allowance, it cannot acquire the standard 

 magnitude, and the butterfly will be dwarfed from the first, 

 and may even be sometimes deficient in one or more of its 

 wings; a circumstance which I have witnessed more than 

 once in butterflies reared by entomologists, who sometimes 

 forget to furnish their caterpillars with food. The same re- 

 marks with respect to growth apply to insects of every kind ; 

 and the fact cannot be better exemplified than in the uni- 

 formity of size in the house-fly (Musca domestica), among 

 which scarcely one individual in a thousand will be found to 

 differ a hair's breadth in dimensions from its fellows. 



It is not, however, by size only that our British white but- 

 terflies may be distinguished ; for they differ very considerably 

 both in the shape of their wings and the markings with which 

 they are embellished. The ground-colour, indeed, is white, 

 but this is, in many instances, dotted, clouded, or shaded with 

 black, and sometimes with other colours, which furnish good 

 characteristic distinctions. I shall now give a short outline 

 of these distinctions, such as may enable young entomologists 

 to determine the species of those which fall in their way in their 

 summer rambles. 



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