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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 presents. 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 be unreliable the 

 instruction which the mind conveys to the eye becomes also 

 unreUable, and the rapidity with which the impression and 

 consequent instruction can be changed will not always com- 

 pete suecessfully 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 [CEdipoda miniatinn, Pallas, 

 and ccErulescens, L.), familiar to all who have traversed the 

 stony slopes of a Swiss mountain. These insects have 

 bright red or blue hind wings, which are displayed only 

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

 concealed vmder the fore wings. The fore wings them- 

 selves are essentially protective in their coloration, absolutely 

 resembling the grey stones amongst which 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 resemblance 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 

 which the insect alights than there would be if such colour had 

 never been displayed. In California I noticed a very similar 

 instance in one of the Arctiada (or Catocalidce), which had pre- 

 cisely similar habits. It frequented the dry stones in the bed of 

 a river left by the shrinking of the water to its summer limits. 

 It had orange hind wings with black bars or mottlings, which 

 were very conspicuous during its short flights, but on alighting 



