MKMUIKS OF THE NATiO.NAL ACADEMY OF SCIENCES. 29 



of this spci'ios. evon in the iJi-cseiu-c of a <;roat propoiulcniiicoof ij'reeii leaves." (Trans. Ent. Soc. 

 Lond., lS!t2, pp. 331, 332.) 



The hirva, says Mr. Poultun. never rested upon tiic lichen itself, but upon the Ijack of the 

 sticks between the masses of liihen. '• This position is eonsisteiit with the larval appearance, 

 which is that of bark partially grown o\ cr with lichen." 



■'There can be little doubt that the larva is inllucnced by the colors of the environment from 

 the time at which it first seeks tlu' older wood, but a certain period is rc(|uired b(d'orc thi' ctlccts 

 become visible." 



"The same relationship between susceptibility and the particidar needs of each species is 

 seen in the effect of an environment of green leaves anil shoots upon (t. (^Kci'cifdlla, O. Jjidt-ntata, 

 and A. hcfuhiria. The first named probably invariably i-ests l)y 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- 

 able 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 tind that, as a matter of fact, it always responds in this 

 way to an environment of the kind described above. B)d,ntat(i doubtless occupies an interme- 

 diate position between the other two species in this respect. The occasions are probably rare, 

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

 finel 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 probatdy the case, however, that 

 the tint which it produces on gi-een leaves and shoots is of great value on a pale j'ellowish-brown 

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

 ])etween the light reflected from this and from green leaves, which explains the similarity in the 

 effects produced upon the larvte."' 



In his essaj' of 1902 Professor Foul ton draws the following conclusions: 



"The other larva? {Smci'intlus^ Sphinx. AtjJ'xt) which I have tested are very inferior to the 

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

 the Indian Spliimjidix. are highh' susceptible. 



"There may be a most extraordinary fluctuation in the amount of susceptibility within the 

 limits of the same genus {('ntdcala and in the pupw of Pup'dio). 



"In Geometrsi alone have distinct green larvse been produced by these experiments. Prob- 

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

 selected at random, all l)ut 1 have proved to be so. 



'"There is no evidence that the results ac(|uired ))y one generation can lie transmitted to the 

 next {Ruinliu CmcaUk). The susceptibilit}- is essentially an adaptiition to the fact that the indi- 

 viduals of each of such species are liable to find themselves in different enviromnents, 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. cr<ds!g<Ata the test for hereditar\- effects 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. jxtpilionarm. 



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



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



"Much effect was produced in about fourteen days in young 2[. iiiimtniiida. 



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



"Much effect was pi-oduced in thirteen (or less) days in j'oung //. aliruptaria. 



"Much effect was produced in seventeen days in young R. cratsegata. 



"'Much effect was produced in eight days in young ^1. hetularia. 



