\ 

 The Origin of the Markings of Caterpillars. 169 



those of another in one form only, we are often 

 unable to ascertain the blood-relationship. 3 In 

 such cases we can only determine the latter from 

 the form-relationship, and as these are not always 

 parallel, any conclusion based on a single form 

 must be very unsound. If, for instance, butter- 

 flies emerged from the egg directly, without pass- 

 ing through any larval stage, a comparison of their 

 resemblances of form would alone be of systematic 

 value ; we should unite them into groups on the 

 ground of these resemblances only, and the 

 formation of these groups would then much de- 

 pend upon the weight assigned to this or that 

 character. We might thus fall into error, not 

 only through a different valuation of characters 

 but still more because two species of near blood- 

 relationship frequently differ from one another in 

 form to a greater extent than from other species. 

 We should have no warrant that our conception of 



8 [Mr. A. G. Butler has recently furnished a good illustra- 

 tion of the danger of classifying Lepidoptera according to the 

 affinities of the perfect insects only, in his paper, " On the 

 Natural Affinities of the Lepidoptera hitherto referred to the 

 Genus Acronycta of authors," Trans. Ent. Soc. 1879, P- 3 I 3> 

 If the author's views are ultimately accepted, the species at 

 present grouped under this genus will be distributed among 

 the Arctiidce, Liparida, Notodontidce, and Noctuce. Mr. Butler's 

 determination of the affinities of the species supposed to belong 

 to the genus mentioned, is based chiefly upon a comparative 

 examination of the larvae, and this is far more likely to show 

 the true blood-relationship of the species than a comparison 

 of the perfect insects only. A study of the comparative 

 ontogeny can alone give a final answer to this question. R.M.] 



