( Ixviii ) 



Tlic ciniKKlinin is in Iji'jiidojitcra a sniall tiilierclc aliove tlie pad lietwecu 

 the claws, boariiii; one l)ristle, si'ldoiu two. It is widely distributed among the 

 l)ad-l)eariiig species, Imt is seldom found in Sjjhingidae {Spliingulufi; llopliocnema). 

 The claws are simple in Spfiiiigulae, not divided or toothed ; they are dilated at 

 tlie hase (PI. XLIV.) The pulvillns (pitlr) varies much in size in Lepidoptera, 

 and is often absent, the ])resence or absence freijuently cliaracterising genera and 

 whole subfamilies, but forming not rarely a distinction only of specific value. 

 Absence of the pulvillus is of common occurrence among Acheronfiinae and 

 AmljuUeiimi' ; while the organ is very seldom obliterated in the other subfamilies, 

 Arctonotus and Euproserpinus being tlie only instances. The paronycliium {par) 

 is membranaceous, ventral and lateral in ]iosition, finely ciliated on the surface, 

 and provided with a more or less long fringe at the edges. Its special shape 

 varies much in insects. It is generally deeply sinuate mesially, and each half ' 

 may be again divided (or perhaps ])roduced) into two lobes. The ])aronychinm 

 of Sphingidae possesses in its most generalised state two slender lobes on each 

 side (PI. XLIV. f. 9. 10), of which tlie upper (or lateral) lobe is generally the 

 longer, very rarely the shorter one. The reduction of the paronychium begins 

 with the ventral lobe (PI. LXIV. f. 11. 12) ; this is always the first to disappear, 

 there being no Hawk Moths which possess the ventral lobe and are devoid of 

 the lateral one. The remaining lobe becomes also gradually shortened, and 

 disappears too, the paronychium then being represented by a small ciliated* 

 membrane, which is often less distinct than in f. 14. 15 of PI. LXIV. The 

 reduction and, practically, obliteration of tlie paronychium occur very often in 

 Acherontiiiiae and Ambulicinae, rarely in the other subfamilies. The diflerence 

 in the paronychium is often employed by us in the definition of genera. However, 

 there are genera {IIi/loic>i!<) in which the absence or presence of a paronychial 

 lobe indicates only sjjccific distinctness, and sometimes not even that. Ilgloiciis 

 perelegans consists of a black-backed and a grey-backed form, which are found 

 in the same country, and are most likely seasonal forms. The black-backed form 

 possesses, like most other Hi/loicKS, a long lateral lobe (PI. XLIV. f. 13), which 

 is represented in the grey-backed form by a short triangular flap (PI. LXIV. 

 f. 14. 15). This difference within the same species is of considerable significance. 

 The case teaches us distinctly that the same kind of character is by no means 

 everywhere of the same taxonomic value. No morphological character is a priori 

 of specific or generic value or indicates a higher category than genus. The 

 taxonomic value of a character has to be studied in each group of s])ecies ; a 

 difference which is insignificant here may be very important there. 



The reduction of the claw-segment — or, rather, of the paronychium and pad, 

 for the claws never disapjiear, nor do they lose the ordinary shape — begins in 

 Sj)hingi(hie with the obliteration of the paronychial lobe. From this second 

 stage lead two paths to the abolition of the pulvillus and paronychium. The 

 ordinary ]>ath is that on which the third stage is represented by a segment 

 without (or with strongly reduced) pulvillus, and with well-developed lateral 

 paronychial lobe ; while the fourth stage is attained when this lobe has also 



