Kusnezov, Die Bedeutung der Färbung der Hinterflügel der Catocala-\\im. | |'7 



protective, aggressive, or attractive purposes, so much has heen 

 said and written that it seems difficult to add any new Suggestion; 

 but there is one point to which only a slight allusion is made in 

 Mr. Poulton's book, and which I do not remember to have seen 

 insisted upon elsewhere, - - viz. the value of bright colours, tem- 

 porarily displayed, as a means of increasing the degree of seeurity 

 derived from protective tints. My attention was lately drawn to 

 a passage in Herbert Spencer's „Essay on the Morals of Trade". 

 He writes: — „As when tasting different foods or wines the palate 

 is disabled by something strongly flavoured from appreciating the 

 more delicate flavour of another thing afterwards taken, so with 

 the other organs of sense, a temporary disability follows an excessive 

 Stimulation. This holds not only with the eyes in judging of 

 colours, but also with the fmgers in judging of textures." -- Here, 

 I think, we have en explanation of the principle on which pro- 

 tection is undoubtedly afforded to certain insects by the posession 

 of bright colouring on such parts of their wings or bodies as can 

 be instantly covered and concealed at will. It is an undoubted 

 fact, and one which must have been observed by nearly all collectors 

 of insects abroad, and perhaps also in our own country, that it is 

 more easy to follow with the eye the rapid movements of a more 

 conspicuous insect soberly and uniformly coloured than those of 

 an insect capable of changing in an instant the appearance it pre- 

 sents. The eye, having once fixed itself upon an object of a certain 

 form and colour, conveys to the mind a corresponding impression, 

 and if that impression is suddenly found to he unreliable the In- 

 struction which the mind conveys to the eye becomes also unreliable, 

 and the rapidity with which the impression and consequent Instruction 

 can be changed will not always compete successfully with the rapid 

 transformation effected by the insect in its efforts to escape. I 

 would take as a simple illustration the case of certain species of 

 large grasshoppers (Oedipoda miniatum, Pallas, and coeruleseens, L.), 

 familiär to all who have traversed the stony slopes of a Swiss mountain. 

 These insects have bright red or blue hind wings, which are dis- 

 played only in flight, and when at rest are folded up and completely 

 concealed under the fore wings. The fore wings themselves are 

 essentially protective in their coloration, absolutely ressembling 

 the grey stones amongst whicrf they rest. When the insect is 

 disturbed, it takes a short and rapid flight, remaining on the wing 

 just long enough to attract the eye to its conspicuous colour, and 

 alights suddenly and abruptly, usually at an angle from its direct 

 line of flight, and is immediately concealed by its protective 

 ressemblance to the surroundings. The very sudden loss of the 

 conspicuous guiding colour of the hind wings so completely deceives 

 the eye that there is much more difficulty in marking the spot on 



