SCALES 



331 



Socket holding the stalk in Galleria 

 mellonella ; B, insertion of the scale 

 of Polyommiatus phloeas. b, Base of 

 scale ; r, holding-ring ; 7U, snrface of 

 wing. (After Spuler.) 



giving rise to metallic " interference-colours." The walls of the 

 scales are themselves, in some cases, tinted with pigment. It is 

 said that some of the scales contain air, and that the glistening- 

 whiteness of certain scales is due to this. The exposed surface of 

 the scale usually differs from the 

 surface that is pressed down on 

 the wing in being delicately and 

 regularly striated ; the colours 

 of the upper and under surfaces 

 of a scale may also be quite 

 different. Scales are essentially 

 of the nature of hairs, and all 

 the transitions between hairs and yib. 172. — insertion of scales, a, 

 true scales may be found on the 

 wings of certain Lepidoptera that 

 bsar both hairs and scales, e.g. 

 lihpmia. It has been calculated 

 that there are a million and a half of scales on the wings of an 

 individual of the genus Morplw. The scales are arranged on 

 the wing in an overlapping manner, somewhat like slates on the 

 roof of a house. Each scale has a short stalk, and is maintained 

 in position by the stalk fitting into a cavity in a projection of 

 the wing-membrane (Fig. 172). 



Androconia. — The males of numerous butterfiies possess 

 scales peculiar in kind and various in arrangement. They may 

 be either irregularly scattered over the wing, or they may form 

 very complex definite structures (Fig. 173). They were formerly 

 called " plumules," but Scudder has replaced this name by the 

 better one, "androconia." The function of the androconia is 

 still obscure. An odour is believed to be connected with them. 

 Thomas supposes ^ that these scales are hollow tubes in connec- 

 tion with glands at their bases, and that matter secreted by the 

 glands passes through the scales and becomes diffused. In 

 nearly all Lepidoptera it is the male that seeks the female ; if 

 therefore odorous scales were present in one sex only we should 

 have supposed that this would have been the female rather than 

 the male. As, however, the reverse is the case, the function of 

 the androconia is supposed to be that of charming the female. 

 Scudder considers that the covering part of the androconial 

 1 Amer. Natural., xxvii. 1893, p. 1018. 



