146 MOUNTAIN AND MOORLAND 



pendently but harmoniously. Like a Wasp, a Dragon 

 Fly can fly tail foremost. The perfection of the flight 

 is associated with the habit of catching insects on the 

 wing, and in this the keen eyesight is also of vital 

 importance. The number of facets and lenses in each 

 compound eye varies from 10,000 to 28,000; and the 

 range at which movements can be detected is said to 

 be up to ten to twenty yards, the limit for other insects 

 being about six feet. They are large-brained, effective 

 creatures. 



Another attraction is the colour of the body, for 

 pigmentation combines with physical structure with 

 extraordinarily brilliant results. In red blood we have 

 to do with pigment colouring; in the mother-of-pearl 

 of a shell we have to do with rainbowlike physical 

 colouring (the pounded shell is simply white powder) ; 

 in the scales of the wings of Butterflies and in the 

 feathers of the Peacock's tail we have a combination 

 of pigmentary and physical colouring, and the Dragon 

 Flies show the same. There are really splendid dis- 

 plays of green, blue, violet, purple, red, orange, and 

 yellow in different species, and the metallic sheen 

 recalls Tennyson's description of "bright plates of 

 sapphire mail." The effect is enhanced by the large 

 gauzelike, unfolded wings and by the glowing eyes. 

 Dragon Flies are able to look after themselves, though 

 birds and trout levy toll, and they can afford a good 

 deal of self-advertising. Brilliant colours are charac- 

 teristic of safe animals. Moreover, in spite of their 

 frequently large size and their conspicuousness of 

 colouring, Dragon Flies have in their masterly flight 

 a baffling way of disappearing and reappearing in 

 the air. 



