312 Professor E. B. Poulton on colour-relation 



the experiment on this and other suitable larvae on the 

 first opportunity. 



I propose to state the results of these experiments 

 forthwith, referring to the plates which accompany the 

 paper. Hence it will be possible to gather the conclusions 

 by looking at the few first pages, while those who desire 

 to study the evidence in detail will find it recorded in the 

 later part of the memoir. 



The first larva which appeared suitable for the purpose 

 Avas Odontopera bideniata, and Mr. G. T. Porritt very kindly 

 consented to look out for ec^gs. Mr. Porritt had himself 

 suggested to me that the larva would probably prove to 

 be especially suitable for the purpose of this enquiry, and 

 he wrote on May 9th, " the larva varies so very much in a 

 wild state according to its food, that I fancy it will form an 

 interesting subject for your experiments." * On May 9th, 

 1893, he kindly sent me from Huddersfield a batch laid by a 

 single female, and, on June loth, a second consignment laid 

 by two females, from Sledmere on the Yorkshire Wolds. 

 The first set afforded the material of Experiments I to IX 

 (including Va) described in this paper. The second mixed 

 set formed the subject of Experiments X to XVIII. 

 The chief results of both experiments will be gathered by 

 a glance at Plate XVI, in which figs. 1 to 5 represent 

 larvsefrom the first set of eo^gs, fisjs. 6 to 11 larvfe from the 

 second set. At the same time results like those shown in 

 the former figures were produced in larvae of the second set 

 and like those in the latter figures, in larvge of the first set. 



The detailed account of the experiments shows the 

 number of days which elapsed before the influence of each 

 environment became visible, and the time which was 

 necessary in order to produce the full effect. A very large 

 number of records proves that the larvse, in the great 

 majority of cases, rested by day upon the object which 



* Dr. T. A. Chapman wrote to me (June 14, 1903), concerning the 

 forms and habits of bidentata :~" About fortj^ years ago, I took 

 three or four beautifully green latticed larva? off the lichen-covered 

 trunk of an old alder-tree in Glen Messen (Argyleshire). They 

 were quite new to me, and though very like (of course) bidentata, 

 I thought they must be something else, a lichen-feeder. When they 

 produced bidentata, I got no further than wondering whether bidentata 

 was sometimes a lichen-feeder. I remember well their resting-place 

 was near the ground, many feet from any leaves, — as long a journey 

 for feeding as the larva of Aprilina makes," 



