TRIFID.E. 223 



is pale throngliout, with only one bristle on each tubercle." 

 "The Q^^ is laid solitarily and is indeed very much like that 

 of jm." 



In curious contrast to this division into three groups 

 mainly by the structure of the pupa, is the result of examina- 

 tion of the " anal appendices," " anal armature," or " appen- 

 dices ancillary to generation," as the curious structure of 

 claspers in the anal segment of the male moth is variously 

 entitled. Mr. F, N. Pierce, who has examined this structure 

 in most of the species, with great cai^e and minuteness, 

 iuform.s me that by it the genus is divisible into three dis- 

 tinct groups : 1st, tridcns, psi, strigosa, alni, menyanthedis, 

 rumicis and mp'iccc (euphorbicv), all of which show very 

 similar structure ; 2nd, leporina, aceris, and ligustri, which 

 again are very similar ; and 8rd, megacephala, which is very 

 distinct from all the rest, "and would probably belong to 

 another genus." Another division of the genus has reference 

 to a point to which I have already adverted — the presence or 

 absence of dorsal crests on the abdominal segments ; but in it 

 sufficient allowance does not seem to have been made for the 

 fugitive nature of these crests or tufts, in certain species. On 

 the whole, it appears best to include all the grey species, as 

 was done by Mr. Stainton, in the genus Acronyda. 



A table of the species may be useful. 



A. Forewings whitish or pale grey. 



B. A black ^ before the anal angle. leporina. 

 B -. A sharp black dagger before the anal angle. 



psi, tridcns. 

 B ^. An obscure black dagger before the anal angle. 



C. Second line distinct ; orb. stig. minute ; ren. stig. 



short. menyanthedis. 



C -. Second line clouded and obscure ; ren. stig. elongated. 



auricoma. 

 B ^. A simple black streak running into the anal angle. 



D. Dorsal half of wing black. alni. 



