THE MOSAIC OF COLOURS 



hardly rises above the level of the surface to which it adheres; 

 moreover, the upper surface is roughened and corrugated, and its 

 colour precisely matches the surrounding bark. Even when removed 

 from the tree, anyone would take the insect to be a lichen-covered 

 fragment of bark. 



The Cicadae are relatives of the Bugs (Plate 29, II, 6). In this 

 group the Thorn Cicadae are worthy of attention. In these little 

 creatures the scutum is developed into two long upward-pointing 

 thorns, so that when they are seated on a twig they are naturally 

 overlooked, as they seem to be simply thorns growing on the twig. 

 Brazil is rich in these remarkable little insects, which assume an 

 incredible variety of forms: sometimes they are adorned with 

 spines, toothed wheels, and other singular outgrowths. 



In the Butterflies Nature seems to have sought to adorn the 

 landscape with jewels, with a species of flying flowers. But the world 

 is no place of peace and tranquillity ; other insects, spiders, frogs 

 and lizards hunt the defenceless butterflies untiringly ; birds capture 

 them in order to devour their succulent bodies, having nipped off 

 their gleaming wings, which for them are only troublesome acces- 

 sories ; and the caterpillars have still more numerous enemies. 

 The Lepidoptera, then, have need of a very thorough form of 

 protective coloration. At the same time, when they sail through 

 the air they must not fail to display their characteristic species-marks. 

 Nature has been able to solve both problems — by applying the 

 protective coloration to one side of the surfaces at her disposal, and 

 painting the other with the signs by which the species is known. 

 In the case of the Butterflies the latter are painted on the upper 

 surface of the wings ; when the insect is at rest it clasps its wings 

 together above its back; the coloured surfaces are concealed, and 

 only the underside of the wings is visible ; and this bears the protec- 

 tive coloration. In the Moths, the vivid colours are set on the upper 

 surface of the hind-wings, in accordance with the different position 

 of the wings. The fore-wings cover the hind-wings as with a roof, 

 and they consequently bear the protective coloration on their upper 

 surfaces. As in the birds, so in the moths and butterflies : the 

 protective coloration, which must be eflfective even at close range, 

 is full of fine detail, while the characteristic signals are applied to 

 wider surfaces, in broad stripes and patches, which can be seen 

 at a considerable distance. 



In all the stages of their development the Lepidoptera profit by 

 protective coloration. The eggs are mostly green, like the leaves on 



p 225 



