122 



Mr. A. G. Butler on the 



of these two families into consideration. The more 

 salient structural differences between these groups, in 

 addition to that noted above, may be roughly summed up 

 as follows : — 



SPHINGID^. 



Palpi short and thick. 



Lateral margins of the hody con- 



tinuous. (Cf. fig. 23.) 

 Posterior legs rather short, thick, 



usually with the tibire smooth and 



armed with short spines. 



Anterior wings broad and trigonate, 

 with short discoidal cell. 



Posterior ivings small, with very 

 short discoidal cell. 



.^GERIID^. 



Palpi medium or long and far more 

 slender. 



Lateral margins constricted behind 

 the thorax. (Cf. fig. 22.) 



Posterior legs long, slender, the 

 tibiie frequently clothed with tufts 

 or masses of hair, always with 

 long spines, the tarsi sometimes 

 adorned with hairy tufts. 



Anterior wings narrow, elongate 

 subpyriform, with long discoidal 

 cell. 



Posterior wings large, with me- 

 dium-sized discoidal cell. 



The differences in the perfect insects therefore cover 

 their entire structure, whilst the larvae of the two families 

 are as unlike, both in aspect and economy, as any two 

 representatives of the same order can well be. 



Some few years ago, when Mr. Stretch, of San 

 Francisco, was in England, he and I were somewhat 

 exercised in mind respecting the affinities of a strange 

 little genus of Clear-winged moths from the New World. 

 This genus, Avhicli I subsequently diagnosed under the 

 name of Acridura (Ann. and Mag. Nat. Hist. 4th ser., 

 vol. XV. p. 398), and referred with some misgivings to 

 the Zygmnoid ArctiidcB, is without doubt an aberrant 

 ^fjeriid allied to Arauzona, and combining the charac- 

 ters of the Clear-wings with those of the Pijrales and 

 Gelechiid(B. 



A careflil study of all the genera which seemed to be 

 allied to Acridura (figs. 5, 6) has manifested a gradation of 

 structure fi'om the j^geriidce. to the Py rales on the one hand, 

 and from the jT^geriidce to the GelechiidcB on the other. 



Before entering into identities and similarities of struc- 

 ture in the imago, it is, of course, extremely important to 

 ascertain whether the larva? of these three groups exhibit 

 any similarity in general structure and economy. I 

 have, therefore, examined into the characters as given 



