1S65.] 199 



H. tessellaris, mature larva. H. Harrisii, mature larva. 



Now if, in the imagos of any two iusects. we found constant distinc- 

 tive characters one-quarter as strong as the above, no entomologist 

 would hesitate for a moment to pronounce them distinct species. For 

 example, Colias PliilodiceGoAt. is universally, and with justice, allowed 

 to be distinct from C. Eurytlieme Bdv., although the only constant 

 character that separates them is, that the first has sulphur-yellow wings 

 and the last orange-colored wings. Yet how slight is the difference 

 between sulphur-yellow and orange-color in these two species, when 

 compared with the differenceT between the black pencils of tessellaris 

 and the orange-colored or milk-white pencils of Harrisii ! And how can 

 we consistently rely upon a single constant character to separate two 

 imagos, if we refuse to acknowledge the validity of four constant dis- 

 tinctive characters to separate two larvae ? 



It is easy to say that one of these two forms is a mere " larval vari- 

 ety" of the other; (see Proc.&c. III. p 586;) but those who use such 

 language misunderstand the very meaning of the term " variety." 

 True it is that many larvae vary astonishingly; but then in their case, 

 as in every ordinary variety, we find the intermediate grades also. 

 While here, as regards the i'onr distinctive characters pointed out above, 

 out of scores of specimens of the mature or nearly mature larva) that I 

 have examined, I have not found a single one that presented any inter- 

 mediate grade whatever. 



No entomologist hesitates to consider two imagos as distinct species, 

 merely because the larvae are undistinguishable. In many families, 

 indeed, e. g. Ci/7iij)iclse, Aj)i<lse and Muscidse, very many larva3 bear so 

 close a resemblance to each other, that he would be a bold man who 

 pretended to distinguish them. Why then refuse to consider two well 

 characterized larvae, like tessellaris and Harrisii, as distinct species, 

 merely because their imagos are undistinguishable? Why lay all the 

 stress upon the characters of the imago, and none at all upon those of 

 the larva or pupa? This is as irrational, as if an entomologist were to 

 cut off and throw away the wings and legs of every imago which he is 

 studying, and persist in classifying it from the consideration of its body 



