The Zoologist — January, 1868. 1045 



7. Nolodonta diclcca and N. dictceoides I believe it possible to 

 separate these two species when in perfect condition ; but it is a matter 

 of great difficulty, unless to those who have made the subject their 

 especial study : it seems to me that Haworth was unable to separate 

 them, and that both species are included under his Bombyx tremula: 

 the distinction between the two has not been made perfectly clear to 

 my apprehension by the descriptions, yet so early as the time of 

 Linneus two species were recognized, Bombyx dictaea and B. tremulus; 

 but Haworth combines these names under that of Tremulus, and 

 Doubleday under that of Dictasa: it is quite possible that it was 

 intended thus to denominate the N. dictaea and N. dictaeoides of 

 our modern nomenclature. Be. this as it may, the similarity of the 

 two species is really marvellous, and nothing but a perfect know- 

 ledge of their larva? could induce anyone to separate them : through 

 the kindness of friends I have been supplied with the larvae of 

 both, and have described them with care ; they are abundantly 

 distinct, and cannot be combined, unless by the admission of the 

 hypothesis, hitherto universally rejected, that there may exist per- 

 manent variations in the larva parallel to those hitherto supposed to 

 be confined to the imago. 



8. Acronycta Psi and A. tridens. — In this case the exact similarity 

 of the two perfect insects is admitted on all hands. Haworth says of 

 Tridens, "Too much like the preceding (Psi), and almost the same, 

 but has a different larva." Haworth, however, in attempting their 

 differentiation falls into a very common error : he says, " The colours 

 (of Tridens) are always paler; the hind wings are whitish or white: " 

 thus apparently referring to the males of both species. The larvae are 

 entirely different, and I have taken great pains to describe both from 

 nature. 



9. Noctua fesiiva and N. conflua. — Here we have a pair which 

 Guenee separates by an intervening species (Noctua collina) : he makes 

 no allusion to the similarity of the two, but quotes the Vienna Cata- 

 logue, Hiibner, Haworth, Treitschke aud Godart as the authorities 

 for the one ; Treitschke, Freyer, Duponchel, Boisduval and Herrich- 

 SchaefFer as authorities for the other: I possess a fair series of both; 

 they vary infinitely, and vary almost precisely in the same way, 

 exhibiting similar colours and similar markings in their variation ; yet 

 there is no character, so far as I can ascertain, that belongs exclusively 

 to either, and I have never yet met with an entomologist who, after 

 inspecting my series, was perfectly convinced of their distinctness. 



