256 Mr. G. F. Hampson on the 



Mr. H. G. Dyar ^, who has worked out Prof. Comstock's 

 system in relation to the setiferous tubercles of the larvas ; 

 and it seems to me that a better primary character is to be 

 found in the migration of vein 5 of the fore wing from its 

 original position at the middle of the discocellulars towards 

 either the lower or upper angles of the cell, as used by myself 

 in my ' Moths of India ' f. Tliis, indeed, is practically 

 admitted by Prof. Comstock himself, for he says, at p. 45 of 

 his paper : — 



" The loss of the frenulum in certain Frenatse renders 

 necessary the use of some other character or characters by 

 the systematists as recognition characters." 



And at p. <S9 : — " And in the Drepanida, where the frenu- 

 lum is usually wanting, it persists in one sex in certain 

 genera." It would be more correct, however, to say that 

 the frenulum is usually present in both sexes, but wanting in 

 several genera. Whilst of vein 5 of the fore wing he says at 

 p. 76: — 



^' The union of vein Vi [vein 6] with radius [the subcostal 

 nervure] and of vein V3 [vein 4] with cubitus [the median 

 nervure] after the abortion of the base of the media [the 

 radials] is what would be expected. But in which direction 

 would one expect the base of vein V2 [vein 5] to migrate ? 

 Occupying an intermediate position between radius and 

 cubitus, it may go either way. It is like a stream in the 

 middle of a level plain, a trifle may change its course. And 

 thus we find that in some families it migrates towards the 

 cubitus, making this vein apparently four-branched, whilst in 

 other families it goes towards the radius, leaving cubitus 

 apparently three-branched. This difference may be looked 

 upon as a difference in kind of specialization, and is frequently 

 of high value as indicating a dichotomous division of the line 

 of descent. It is obvious that in a family where vein V2 has 

 migrated far towards cubitus, and has thus established its 

 chief source of air-supply in that direction, it is not probable 

 that genera will arise in which vein Vg is more closely united 

 to radius than to cubitus. To resume the figure, the plain 

 through which the stream is flowing is an elevated plateau, a 

 pebble may determine which of two slopes it shall descend, 

 but when started down one it cannot traverse the other." 



A more curious instance of the failure to a]:)ply his own 

 principles is to be found on pp. 97, 98, and 108, where the 

 ZygEenidee are divided into tvv^o sections falling into widely 



* Ann. N. Y. Acad. Sci. viii. p. 202. 

 t 'Motlis of India; vol. i. p. 9 (1893). 



