3i6 Insects and their Surroundings 



with their colour and appearance. Numerous species, 

 spending their Hves above ground, in open situations 

 where they are subject to attack by hungry vertebrate 

 and other enemies in search of food, harmonise in 

 aspect so closely with their surroundings as to be 

 concealed. For example. Moths, Grasshoppers, and 

 Lantern-flies, habitually rest with hind-wings folded 

 and concealed beneath the fore-wings. The hind- 

 wings, invisible when the insect is at rest, are often 

 brightly coloured — red, blue or yellow ; the fore-wings 

 on the other hand are usually mottled with various 

 shades of brown or grey, and are quite inconspicuous 

 as the insect sits on a rock or a tree-trunk. Such 

 cases oi protective resemblance are doubtless due to the 

 action of natural selection, the individuals correspond- 

 ing best with their surroundings having been preserved 

 through many generations. In a previous chapter 

 (p. 138) reference was made to the dark coloration of 

 moths in cool and damp districts. It has been sug- 

 gested that this is not due simply to the effect of cold 

 or moisture in inducing the formation of dark pigment, 

 but also to the selection of the darkest individuals 

 through the surfaces where they habitually rest being 

 necessarily darker than in a dry region. Studying 

 the wing patterns of Butterflies we find that the front 

 wings do not differ from the hind-wings ; the upper 

 surface of all four is usually brightly coloured. 

 Butterflies, however, rest as a rule with the wings 

 folded over the back so as to expose the lower surface 

 to view, and this is usually protectively coloured 

 with a mottled pattern of brown or grey. An 

 observation made on a common African butterfly — 

 Haiuani/midn dcvdaltis — shows the importance of the 

 nature of the wing markings in relation to the resting- 

 attitude. In West Africa this insect rests with the 

 wings folded over the back, exposing the tawny 



