MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 29 



of this species, even in the presence of a great preponderance of trreen leaves." (Trans. Ent. Soc. 

 Loud., 1S1»2, pp. 331, S3-2.} 



The hirva, says Mr. Poulton. never rested upon the lichen itself, hut upon the back of the 

 sticks between the masses of lichen. "" This position is consistent with the larval appcanuu'e, 

 which is that of bark partially grown over with lichen."' 



'"There can be little doubt that the larva is influenced by the colors of the environment from 

 the time at which it first seeks the older wood, but a certain period is required before the etiects 

 become visible." 



'"The same relationsliip between susceptil)ility and tlie particular needs of each species is 

 seen in the effect of an environment of green leaves and shoots upon (r. ijaei'cifolia, O. hidcntdta^ 

 and A. hetuhiria. The first named probably invariably rests tiy day, except for a brief period 

 after leaving the egg, upon the older wood, and the power of adjustment to leaves and young- 

 shoots, being altogether useless to it, has never been acquired. The last named, with its remark- 

 aVjle range of food plants, including man}- such as broom or rose, in which green shoots are a 

 prominent feature, is frequently in a position in which a green color could best conceal its nearly 

 smooth and cylindrical form; and we find that, as a matter of fact, it always responds in this 

 way to an environment of the kind described aT)ove. Bhhntata doubtless occupies an interme- 

 diate position betw-een the other two species in this respect. The occasions are prol)ably rare, 

 but not altogether wanting, in which it is compelled to develop in a green environment. We 

 find that it has the power of making some considerable approach toward such surroundings, but 

 not of attaining any high degree of resemblance to them. It is probably the case, however, that 

 the tint which it produces on green leaves and shoots is of great value on a pale jellowish-brown 

 bark, which may often form its environment; and it may well l)e that it is something in common 

 between the light reflected from this and from green leaves, which explains the similarity in the 

 effects produced upon the larva\" 



In his essay of 1902 Professor Poulton draws the following conclusions: 



"The other larvse {SmerinfliKs^ Spht'n.v, Aylin) which 1 have tested are very inferior to the 

 genus Catiirala in this respect, but from what Colonel Swinhoe tells me it is evident that some of 

 the Indian SpliiiKjidte are highly susceptil)le. 



"There ma}' be a most extraordinary fluctuation in the amount of susceptibility within the 

 limits of the same genus {Ckdacahi and in the pupa; of Papilhi). 



"In Geoinetrx alone have distinct green larvte been produced by these experiments. Prob- 

 ably the great majority of these larva; are sensitive. Out of 11 species, many of which were 

 selected at random, all but 1 have proved to be so. 



"There is no evidence that the results acquired by one generation can be transmitted to the 

 next {Biu/ij'd, Crocallis). The susceptibility is essentially an adaptation to the fact that the indi- 

 viduals of each of such species are liable to find themselves in different environments, so that 

 any bias from the experiences of the past would of course be injurious, unless the earlier and later 

 surroundings happened to correspond. 



" In the case of B. erat^gata the test for hereditary etiects was as complete as it could be in 

 one generation. 



"Concerning the time which is necessary before the color changes begin to appear — 



"Some effect was produced in eight days in young G. pap'dionariu. 



" Some effect was produced in eight days in young C. electa. 



" Much effect was produced in twelve days in young C. elingmxria. 



"Much effect was produced in about fourteen days in young M. montanata. 



"Much effect was produced in about eleven days in young C. elocatu. 



"Much effect was produced in thirteen (or less) days in young IT. ahraptarla. 



"Much effect was produced in seventeen days in young R. cndn^gata. 



"Much effect was produced in eight days in young A. hefnlcrid. 



