220 THE COURTSHIP OF ANIMALS 



the purpose of a resonator, increasing the volume of the 

 sound produced by the stridulating organ, which consists 

 of a series of ridges placed on each side. The noise which 

 this mechanism produces is, as might be supposed, con- 

 siderable. It is curious to remark that in this group 

 the females are more vividly coloured than the males. 

 In the case of one South African species — Pneumora 

 scutellaris — this coloration is so extravagant that she has 

 been said to look as if " got up " for a fancy-dress ball 

 (Plate 33, Fig. i). Her ground colour is of a light green, 

 with pearly-white markings, surrounded by an edging of 

 magenta ; the white areas are very numerous. The face 

 has magenta patches, and numerous, tiny, pearly-white 

 tubercles, each of which, when placed on a green part, 

 is surrounded by a ring of mauve. This scheme of 

 coloration distinguishes her as one of the most remark- 

 ably coloured of insects. But to what are we to attribute 

 these hues ? Sexual Selection will not explain them, 

 and it seems unreasonable to regard them either as afford- 

 ing a protective or a warning coloration. They may 

 then, perhaps, be allowed to rank as another instance 

 of unchecked variation in the direction of vivid colouring, 

 such as has been already described as occurring both 

 among birds and other animals lower in the scale. 



In the Locustidae the ear is placed on the side of the 

 front leg and the rim surrounding it may either take an 

 oval shape or close up to form a slit. The air necessary 

 for the efficient action of the acoustic apparatus is admitted 

 through a gaping hole in the side of the body, above the 

 base of the leg, an arrangement not met with among 

 any other insects. The musical apparatus of these 

 insects differs from that of the Acridiidae, for it is 

 formed only by the wing-cases, and not by the wing- 



