370 Explanation of Plates. 
Fie. 6. About half-grown larva showing the effect of an environ- 
ment of bark covered with bluish-green lichen, probably 
Physcia pulverulenta. This typical result of Experiment 
XIII was painted on August Ist. 
About half-grown larva showing the effect of the environ- 
ment last described. This second typical example of the 
results of Experiment XIII was painted on August 3rd. 
8. Nearly mature larva showing the effect of an environment 
of bark covered with orange lichen, perhaps Physcia 
parietina, probably combined with P. pulverulenta. This 
typical result of Experiment XIV was painted on 
August 4th. 
9. Nearly mature larva showing the effect of the environment 
last described. This second typical example of the 
results of Experiment XIV was painted on August 5th. 
10. Nearly mature larva showing the effect of an environment 
of lichen-covered sticks, The lichen was probably 
Ramalina farinacea. This typical result of Experiment 
XV was painted on August 10th. 
11. Nearly mature larva showing the effect of the environment 
described in Fig. 6. This third typical example of the 
results of Experiment XIII was painted on August 31st. 
Comparing the last six figures of larve together with the repre- 
sentation of the various forms of lichen-covered bark employed in 
the experiments, it is seen that there was no special resemblance to 
the characteristic features which distinguished one form of environ- 
ment from the others. Thus the orange colour of the lichen did not 
produce any corresponding effect upon the larva shown in Figs. 8 
and 9. 
The whole results prove that bidentata is a larva with remarkable 
susceptibility to the colour of its environment. In this respect it 
is equal to the most sensitive of all larvae hitherto tested—-dAmphi- 
dasis betularia. The latter is more susceptible to green leaves and 
ss 
shoots, becoming bright green when restricted to their influence. 
When exposed to lichen-covered bark, however, bidentata was shown, 
in Experiments XII to XV, to be far more sensitive. 
EXPLANATION OF PLATE XVII. 
Results of Experiments in 1893-4 upon the colour-relation between 
the larvee of Gastropacha quercifolia and their environment. 
All the figures are of the natural size, and all represent the 
normal resting position, except that the larve more frequently rest 
