THE EXTERNAL STRUCTURE OP THE LEPIDOPTEROUS LARVA. 43 



form larvae " to the cylindrical larvae of certain Coleoptera (weevils, etc.), 

 as well as to those of Diptera, Lepidoptera, and Hymenoptera, con- 

 sidering that the larvae of all these were the result of adaptation, and 

 were "derivatives of the primary ' campodea ' type of larva." 

 Lubbock practically adopted* Brauer's views in 1873. In 1895, 

 Packard consideredf that, " while the origin of the eruciform 

 larvae of the Cerambycidae. Curculionidae, Scolytidae, and other 

 wood-boring and seed-inhabiting and burrowing coleopterous larvae in 

 general, is plainly attributable to adaptation to changed modes of life, 

 as contrasted with the habits of roving, carnivorous campodeiform 

 larvae, it is not so easy to account for the origin of the higher mefea- 

 bolous orders of Diptera, Lepidoptera, and Hymenoptera, whose larvae 

 are all more or less eruciform." He supposes them all to have arisen 

 independently from groups belonging to the Neuroptera (in the modern 

 sense), or to some allied but extinct group. 



In 1895, we suggested! that the earliest forms of lepidopterous 

 larvae were hidden, and probably internal feeders. This view is not 

 shared by Packard, who suggests that the earliest type was " allied to 

 some Tineoid which lived, not only on land, but on low herbage, not 

 being a miner or sack-bearer." This conclusion is arrived at by his 

 consideration of the remarkable changes in form of certain Tineoid 

 mining larvae, described and figured by Chambers|| and Dhnmock.§ 

 These larvae were those of the Lithocolletids, Gracilariids, etc., and 

 we quite agree that these apodous forms of mining larvae are the 

 result of adaptation to their habits. Our own idea of the ancestral 

 form was, and is, one more closely resembling those of Hepialus, 

 Cossus or Zeuzera, but the point matters little. What most authorities 

 are agreed upon is — that by the time the ancestral larva was essen- 

 tially lepidopterous, it was provided with prolegs that bore terminal 

 crochets or hooks, and with simple fleshy warts or tubercles bearing 

 simple hairs. The various forms in which the crochets are now 

 arranged on the prolegs, and the many modifications which one finds 

 in the arrangement and character of the piliferous tubercles, must be 

 looked upon as more recent developments. 



Meldola first suggested^" that the green colour of many cater- 

 pillars was due to the presence of chlorophyll in their tissues, and the 

 matter was carried much further by Poulton* in his experiments on 

 the larvae of certain species of the genus Smerinthns. Packard thinks 

 that the cuticle was at first colourless or horn-coloured, and suggests 

 that " after habitually feeding in the direct sunlight on green leaves, 

 the chlorophyll thus introduced into the digestive system, and into 

 the blood and the hypodermal tissues, would cause the cuticle to 

 become green," whilst, afterwards, " by further adaptation and by 

 heredity, this colour would become the hue common to caterpillars." 

 In view of Poulton's more recent experimentsf it would not do to 

 labour this point too much, and we are inclined to agree with him, 

 that the effect is rather " phytoscopic " than "phytophagie," inas- 

 much as the colour of the surface of the leaf, rather than its substance, 



* Origin and Metamorphosis of Insects, 1873. f Bombycine Moths of America, 1895. 



I Entom. Record, etc., vii., p. 6. 



|| American Naturalist, iii., 255-262 ; Psyche, ii., 81, 137, 227, etc. 



§ Psyche, Hi., pp. 99-103. M Proc. Zool. Soc. of London, 1873, p. 159. 



* Proc. Boy. Soc. Lond., 1885, p. 269. t Trans. Ent. Soc. Lond., 1892, pp. 294 et seq. 



