SPECIFIC DIFFERENCES IN LITHOSIDiE. 



83 



Such, then, is our knowledge. It would be interesting to 

 know why Mr. Barrett puts Guenee's name before Gregson's, 

 and also why he is so dogmatic in using the word " supposed ; " 

 it evidently is not accepted, by Mr. Tutt's remarks made after 

 Mr. Barrett's statement. 



I had long wished to examine the structure of the genitalia, 

 and very gladly accepted Mr. G. 0. Day's kind offer to send me 

 worn males. These I have very carefully examined and com- 

 pared, but, alas ! the result is a negative one. I can see no form 

 of difference between the two. Some may be inclined to say: 

 " Why, this at once settles the point; the species has been doubted 

 all the way through ; now the genitalia being identical confirms 

 the well-grounded suspicion." But it is not so, nor is it wise to 

 jump to conclusions from negative results. During my investi- 

 gations I have repeatedly found very closely connected species 

 possess organs so similar that I have found it impossible to dis- 

 tinguish any difference, although the imagines may have an 

 abundant difference in wing-markings and breed true to type ; 

 also that the larvae may differ. One point of differentiation is 

 not sufficient, and although I regret that I have failed to decide 

 this knotty question by genitaHa, it will want stronger evidence 

 than has been brought forward in the bare statements of the 

 writers quoted, to convince me that sericea is identical with 

 complana. 



I shall presently show that there is practically no structural 

 difference between the genitalia of complana, sericea, and pyg- 

 mceola ,- and as all are agreed that the latter is a distinct species 

 from either of the former, although having similar genitalia, 

 therefore there is no proof of the identity of complana and 

 sericea because the genitalia in these two species agree. 



Whether the genitalia may be used exclusively for classifica- 

 tion or not, it seems to me, will depend upon how far it aids other 

 means. In this paper I do not intend to attempt this, but give 

 the results as I find them, and leave it for others to make what 

 use they like of them. The method I have adopted is to take 

 the simplest form as the start, and gradually lead up to the 

 highest or most complicated form. The portions I compare 

 consist of the harpes, situated at either side of the body ; the 

 claspers, which are the hooks inside the harpes ; the uncus, a 

 large spine on the dorsal portion which projects between the 

 harpes and which, as many of the preparations are flattened, is 

 bent sideways ; and, lastly, a most important organ connecting 

 the base of the harpes which I call the juxta. 



Lithosia mesomella (Fig. 1).— Harpes are squared at the apex ; 

 the claspers are broad for three parts, then narrowed off to a 

 chitinous point ; the uncus is slightly contracted near the tip, 

 the juxta is wide, bent towards the centre, and corners without 



the acute angle. 



H 2 



