42 BRITISH LEPIDOPTERA. 



with dorsal and lateral humps, so that they may assimilate more 

 readily with the colour of the bark of the tree upon which they rest, 

 and to small twigs bearing leaf-buds, etc. But such larva as are 

 particularly protected in this manner do not lead such exposed lives as 

 do those which, by the modification of the tubercles and setae of the 

 more generalised larv, have developed conspicuous spines, pencils of 

 hairs, etc., or those which, by the development of bright warning 

 colours, ocellated spots, etc., present an inedible, or even dangerous 

 appearance to the avian, and numberless other, enemies which surround 

 them on every side. 



Those larvae which live upon trees, and trust for their escape to 

 their resemblance to pieces of stick, etc., are sometimes remarkably 

 tuberculated. This is particularly noticeable in the Geometrids and 

 Notodonts. On the other hand, those larvae which are arboreal, but 

 which trust for their concealment to leafy abodes which they make and 

 in which they dwell such as the Tortricids, Pyralids, etc. have 

 retained, in many ways, much more generalised forms of larvae, both 

 as regards colour, markings and tubercles. The adaptation of exposed 

 larvae to their surroundings is also very remarkably illustrated in the 

 case of many "plume " larvae. No better illustration is needed than the 

 similarity of the dermal clothing of the larva of Aciptilia galacto- 

 dactyla to the woolly covering of the underside of the leaves of burdock 

 (Arctium lappa), whilst Miss Murtfeldt quotes a parallel case among 

 the American " plumes," stating (Psyclw, iii., p. 390) that " there is a 

 very close imitation in the dermal clothing of the larvae of Leioptilus 

 sericidactylus to that of the young leaves of Vernonia, on which the 

 spring and early summer broods feed." 



The inedible nature of hairs needs no demonstration. That many 

 birds are able to eat hairy larvae is no detraction from the general 

 principle. The fact that some birds do eat hairy larvae leaves un- 

 answered the fact that there are numbers of birds that cannot ; and, 

 undoubtedly, many small insectivorous birds that would eat a Tortricid 

 larva with gusto, and make no objection to its simple setiferous hairs, 

 would object to a larva of Arctia caia, or that of Acronicta leponna. 

 We may take it for granted that the ultimate use of spines and 

 hairs is for protection, and further, that they have been stimulated in 

 their development by natural selection, indicating to insectivorous birds 

 that the bristly armature is inedible ; yet it seems that we have hardly 

 reached the bottom of the question, if we look upon the special develop- 

 ment of the setae and spines as due to protective needs, arising 

 either from the attacks of birds or parasitic insects, but that we yet 

 require some explanation of the initial cause of the development of 

 such spines and specially developed hair structures. 



Fritz Miiller, in 1864, maintained that the so called metamorphoses 

 of insects, in which these animals quit the eggs as grubs or cater- 

 pillars, and afterwards become quiescent pupae, incapable of feeding, 

 was not inherited from the primitive ancestor of all insects, but was 

 acquired at a later period. Brauer, in 1869, divided the larvae of 

 insects into two groups, the " campodea " form and " raupen " form. 

 In 1871, Packardf adopted these views, and gave the name of " eruci- 



* " Betrachtungen iiber die Verwandlung der Inseckten, etc.," Verh. K. K. Zool. 



bot. Get. Wien, 1869. 

 f American Naturalist, September, 1871. 



