81 THE CAUSES WHICH PUOPAGATE 



Dermal wing- tints^ in the ease of the rapacious grasshoppers, 

 sometimes possess a smooth beauty like stained glass, enhanced 

 by a transparency to light which serves to throw the reflections 

 from the crimson and yellow scales on the handsome hind wings 

 of moths quite into shadow. In either case likewise this bright 

 colouring is associated with protected areas. The elytra or fore- 

 wings of the afore-mentioned locusts, which they employ to con- 

 ceal their charming colour-wings, mock the dark patches of 

 fibrous moss they frequent, while their equivalents in the 

 nocturnal moths are branded on their supex'ior surface with the 

 protective lichen-marks and tints of the group. But although 

 bright colouring or metallic marking is not rare in this group, 

 the Orthoptera are not often so sexually distinguished, a cir- 

 cumstance pi'obably owing to their endowment with excellent 

 organs of music ; a few cases nevertheless occur, as one of the 

 Saddled Leaf-crickets [Ephijipigeni rugoslcollis, Ser.), where the 

 male is described as fawn-colour and the female is green ; and 

 that of a North American cricket {(Ecanthas iiiveus), where the 

 male is ivory-white and the female yellowish or greenish. 



Beetles are distinguished among insect orders by the high 

 degree of induration of the integumental parts exposed in 

 repose, and we perceive the external cuticle frequently chitinised 

 or horny as if it had been exposed to the influence of a petri- 

 fying sjjring or hoar-frost. This process of hardening may be 

 viewed in various stages of completeness, in the semi-terrestrial 

 grasshopper and bug tribes, which only occasionally use their 

 organs of flight, and everywhere harmonises with the habit of 

 the species, conferring, as it does, a heavy movement where mo- 

 mentum is acquired at the expense of agility. In this latter 

 respect, its influence on the anterior members of aerial locomo- 

 tion is noteworthy ; these present every nuance, from the limber 

 wings of the light butterfly to the simply expansile wing-eases 

 of the beetle, which, in their lowest form, are united together 

 and abbreviated so as to appear but a modification of those 

 excrescences so frequently noticed on parts of the insect thorax, 

 into which the trachea has j^ushed a vesicular ramification. It 

 is consonant, then, that the alar colouring and patterns should 

 reappear on the elytra, and these are sometimes resident on the 

 dermis and sometimes are blazoned on a covering of pile, or 



