( Ixvii ) 



possessed by Campsiogene and Protawliidi/x. Here tlie corresponding spines ai'e 

 slightly thinner than the more distal ones, bnt very little longer, the most 

 basal ones being even shorter than tliese. The comb occurs again in the 

 Sphingidae semanojihorue, especially in the lower forms ; bat tlie bristles never 

 attain the lengtli they have in Ac/wro/it/hiar, resembling always more ordinary 

 spines and becoming gradually shorter (PI. LXIV. p. 8). It will be noticed 

 in the figure quoted that the third row of spines does not reach the base of 

 the segment. 



The hindtarsus is generally longer than the midtarsus, but agrees with it 

 in appearance. The comb, however, is less strongly developed, and is not part 

 of tlie fourth but of the third row of spines, which is very strange, and, like 

 all strange things in morphology, very interesting. The combs of mid- and 

 hindtarsus serve doubtless both the same purpose — we think, of keejjing the 

 abdominal fringe of tlie wing in order, and, in the cJcJ, perhaps also to brush 

 the tuft of the abdominal scent-organ. As the hindtarsus is in a different position 

 to the body and wings, the position of the comb has become altered, or, rather, 

 another row of spines has developed into a comb. As the four ventral rows 

 of spines of the three tarsi are homologous organs, and as the comb of the 

 hindtarsus is homologous to the third row of spines of the midtarsus, we see 

 clearly that the apjiearance of the comb on the hindtarsus is not due to an 

 inner factor of development causing the comb of the midtarsus, developed for 

 some jiurpose, to be repeated on the hindtarsus. It must have been an 

 extraneous factor — i.e. adaptation — which was the cause of the development 

 of the same kind of organ from different sources. 



The second and fourth rows of spines of the first segment of the hindtarsus, 

 or only the fourth, do not reach the base. 



The fifth segment of all tarsi bears some stout and pale sensory hairs at the 

 end on each side close to the ai)ical sjiine, forming often a brusli. There are two 

 long bristles dorsally close to the edge, curving ventrad (PL LXIV. f !• — 15). 

 In a few instances the number of bristles is larger in some individuals, there 

 being occasionally as many as four or five ; but this is quite an exception. The 

 pair of bristles is normal not only for the Sphingiilae, but also for a number 

 of other families. In Butterilies and Skippers we find from four to ten bristles ; 

 in Spliinqiduc, Nortiiidae, Notodoididae, La.-iiocampidae, etc., there are two ; 

 while the bristles are absent or vestigial in I'l/ralidae, Zj/gaenidue, Aegeriidae, 

 Hepialidae, Tineidar, etc. The character is of taxonomic value. TInjrididae 

 with two bristles and I'l/ralidae without them can thus readily be distinguished. 

 In Sattirniidae and Uraniidue the two large bristles are generally accompanied 

 by several smaller ones. 



The claw-segment is one of the most interesting organs of insects, on account 

 of its very numerous modifications. It does not seem to us to have been made 

 use of in systematic works on Ileterocera. The elements of which it is composed 

 are the claw {oti>/chiiim), the false claw (paron'/r/n'/n//), the imd {jM<li:illi(--<); and 

 the empodium. 



