INSECTS. 



105 



To bring this varied organism fully into play, it is necessary 

 that each insect should possess the power of transporting 

 itself with ease to whatever situation its necessities require, 

 and that it should be furnished, for this purpose, with organs 

 of flight adapted to the varying circumstances and requirements 

 of the several tribes. These wings never exceed four in 

 number. In beetles of burrowing habits the upper pair is 

 hard and horny, and serves to protect the softer membranous 

 pair when not in use. The wing-covers or shards (elytra) 

 are expanded in flight, and, by their concavity, help to sustain 

 the insect in the air; hence Shakspeare's description of 



" The shard-borne beetle, with his drowsy hums," 

 is not less accurate than poetical. In other tribes the wings 

 resemble the finest lace ; and in the butterflies and moths they 

 are covered with a mealy substance, which examination under 

 a lens shows to be composed of the most delicate scales, dif- 

 fering in form, in size, and in colouring, and giving to some 

 of these " gilded butterflies" the gorgeous metallic tints for 

 which they are so remarkable. 



" The grand and characteristic endowment of an insect," 

 says Professor Owen, "is its wings; every part of the organi- 

 zation is modified in subserviency to the full fruition of these 

 instruments of motion. In no other part of the animal 

 kingdom is the organization for flight so perfect, so apt to 

 that end, as in the class of insects. The swallow cannot 

 match the dragon-fly (Fig. 83) in flight. This insect has 



Fig. 83. DHAGON-FI.Y, 



