Chap. X.] HYMENOPTERA.— COLEOPTERA. 355 



an extremely brilliant steel-blue, sometimes tinted with 

 vivid green; the male being of a bright brassy color 

 clothed with rich fulvous pubescence. As in this group 

 the females are provided with excellent defensive weap* 

 ons in their stings, it is not probable that they have come 

 to differ in color from the males for the sake of protection. 

 Mutilla Europma emits a stridulating noise ; and ac- 

 cording to Goureau 57 both sexes have this power. He 

 attributes the sound to the friction of the third and pre- 

 ceding abdominal segments; and I find that these sur- 

 faces are marked with very fine concentric ridges, but so 

 is the projecting thoracic collar, on which the head artic- 

 ulates ; and this collar, when scratched with the point of 

 a needle, emits the proper sound. It is rather surprising 

 that both sexes should have the power of stridulating, as 

 the male is winged and the female wingless. It is notori- 

 ous that Bees express certain emotions, as of anger, by the 

 tone of their humming, as do some dipterous insects ; but 

 I have not referred to these sounds, as they are not known 

 to be in any way connected with the act of courtship. 



Order, Coleoptera (Beetles). — Many beetles are col- 

 ored so as to resemble the surfaces which they habitually 

 frequent. Other species are ornamented with gorgeous 

 metallic tints — for instance, many Carabidae, which live 

 on the ground and have the power of defending them- 

 selves by an intensely acrid secretion — the splendid dia- 

 mond-beetles which are protected by an extremely hard 

 covering — many species of Chrysomela, such as C. cere- 

 alls, a large species beautifully striped with various col- 

 ors, and in Britain confined to the bare summit of Snow- 

 don — and a host of other species. These splendid colors, 

 which are often arranged in stripes, spots, crosses, and 

 other elegant patterns, can hardly be beneficial, as a pro- 



61 Quoted by Westwood, 'Modern Class, of Insects,' vol. ii. p. 214. 



