PROTECTIVE MIMICKY. 243 



in tht' same genus with tlic Hnmming-bird Hawk moth. 

 Mr. Ponlton evidently does not take this view of their 

 relationshij), which seems to be mainly founded upon the 

 characters of the lavvw. 



But when we bear in mind the totally different habits of the 

 larvfv of those two insects, which feed upon leaves, from those 

 of other Clearwings which bore in the interior of stems, this 

 difference is not surprising. The Clearwings, therefore, form 

 a group of Lepidoptera, all of which are distinguished by the 

 peculiarity of the defective scaling of the wings. It seems less 

 likely, therefore, that the loss of the scales was due to a need 

 for protection, than if only a few were thus modified ; it is a 

 family character. But even if it were not so, and if only a few 

 Sesiids resembled Hymenoptera, the modification would not 

 be so remarkable as many other divergences from the normal 

 structure of the genus or family that occur ; for in many quite 

 different families of Lepidoptera we have the same tendency to 

 lose the scales : in the Zygfenid;v.\ for instance, and in the 

 Heliconidtw. 



It might be supposed that tlie absence of scales had some- 

 thing to do with the origin of the Lepidoptera from insects 

 without scale-covered wings — the Neuroptera, for instance — to 

 which they are believed to be most nearly allied ; but embryo- 

 logy shows that the loss of scales is a modification, and that 

 the parent form was a lepidoptcrous insect. Mr. Ponlton 

 mentions that the Bee hawk, even when just emerged from 

 the chrysalis, has the wings thinly clad with scales, which fall 

 off directly it begins to fly. In the Currant Clearwiug {Sesia 

 tipuUformis), and in Sesia apifonnis the insect is hatched 

 from the chrysalis free from scales; these are partially formed 

 during the pupal stages, but arrested in development.* 

 * Ami. and Mag. Naf. Hist., Ser. 6th, vol. vi., p. 185. 



