U:q)lanation of PlaUs. 369 



EXPLAXATIOX OF PlATE XYI. 



Eesults of Experiments in 1S93 upon tlie colour-relation between 

 tlie larv« of Odontopera bidentata and their environment. 

 All the figures are of the natural size. 



Fig. 1. Nearly mature larva of 0. bidenfrita showing the eflfect of 

 an environment of black-barked twi^ (Querciis cerris). 

 This typical example of the results of Experiment I wa.s 

 painted by Mr. P. J. Bayzand on July 31st. 1S93. All the 

 larvge figured on this plate were fed upon the leaves of 

 Popnhis nigra, but they nearly always rested by day on 

 the twigs or pieces of bark made use of in the experi- 

 ments here illustrated. The larva represented in this 

 figure is not in its normal diurnal resting position, having 

 been disturbed ; and the same is more or less the case 

 with Figs. 3, 5, 7 and 9. 



2. Nearly mature larva showing the effect of an environment 



of weathered pale grey barkless twigs. This typical 

 example of the final results of Experiment YII was 

 painted on .July 28th, A little earlier the larvie had 

 been rather paler and resembled more closely the majority 

 of the twigs made use of. 



3. Xearly mature larva showLug the efi"ect of an environment 



of dark purplish-brown, glossy twigs, probably of birch. 

 This typical result of Experiment III was painted on 

 July 30th. 



4. Nearly mature larva showing the eflfect of an environment 



of white-spotted, purplish-brown twigs of birch. This 

 typical result of Experiment IV was painted on July 

 30th. Although the details of the environment were 

 not reproduced, the larva was distinctly less dark thali 

 that shown in Fig. 3. 



5. Nearly mature larva showing the eflfect of an environment 



of green leaves and shoots. The food-plant iPopnlus 

 nigra) was emjiloyed for this ptirpose, all dark-barked 

 twigs being carefully excluded. A comparison of this 

 figure with the others on the same plate indicates that 

 the leaves of the food-plant produce no effect when they 

 are combined with dark twigs or lichen-covered bark : 

 while a reference to Experiments I to XT shows that 

 the great majority of the larvae rest by day upon these 

 latter objects in preference to the leaves. This typical 

 result of Experiment YlII was painted on July 31st. 



