72 MIMICRY, AND OTHER PROTECTIVE 



find the greatest amount of conspicuous colour, or at 

 least the most complete absence of protective imitation. 

 The stinging Hymenoptera, wasps, bees, and hornets, 

 are, as a rule, very showy and brilliant insects, and 

 there is not a single instance recorded in which any one 

 of them is coloured so as to resemble a vegetable or in- 

 animate substance. The Chrysididse, or golden wasps, 

 which do not sting, possess as a substitute the power of 

 rolling themselves up into a ball, which is almost as 

 hard and polished as if really made of metal, and they 

 are all adorned with the most gorgeous colours. The 

 whole order Hemiptera (comprising the bugs) emit a 

 powerful odour, and they present a very large propor- 

 tion of gay -coloured and conspicuous insects. The 

 lady-birds (Coccinellidas) and their allies the Eu- 

 morphida?, are often brightly spotted, as if to attract 

 attention ; but they can both emit fluids of a very 

 disagreeable nature, they are certainly rejected by 

 some birds, and are probably never eaten by any. 



The great family of ground beetles (Carabidse) 

 almost all possess a disagreeable and some a very 

 pungent smell, and a few, called bombardier beetles, 

 have the peculiar faculty of emitting a jet of very 

 volatile liquid, which appears like a puff of smoke, 

 and is accompanied by a distinct crepitating explosion. 

 It is probably because these insects are mostly nocturnal 

 and predacious that they do not present more vivid hues. 

 They are chiefly remarkable for brilliant metallic tints 

 or dull red patches when they are not wholly black, 

 and are therefore very conspicuous by day, when insect- 



