162 Dr. H. Eltringham's Further Observations on the 



'-b 



these is plainly visible. The first to arise are the small 

 dark-coloured hairs seen near the middle of the section. 

 These form a core continued throughout the length of the 

 brush, and, unlike the components of the core in the egialea 

 brush, are heavily chitinised from their origin. Surround- 

 ing these are hairs of large diameter, less chitinised, and 

 corresponding -with the yellow hairs of other brushes 

 described. The remainder of the section is seen to be 

 occupied by hairs of relatively small diameter and less 

 distinct outline. These at their origin are scarcely dis- 

 tinguishable from the yellow hairs, though they soon 

 become differentiated by their granular appearance. In 

 PI. XIV, fig. 2, the black hairs have begun to appear at 

 one side and the cuticle of the brush has become thin. 

 Figs. 3 and 4, representing the same structures at higher 

 levels, show an increasing diameter in the hairs of the core. 

 In fig. 5, still higher, the black hairs have become less 

 numerous and those of the core smaller, whilst the granu- 

 lated hairs now betray their purpose as dust producers, 

 breaking up and forming small nodules as in A. ochlea. 

 Fig. 6 is a section taken still nearer the end of the brush. 

 The black hairs have nearly died out, the core hairs are 

 much reduced in diameter, and the dust hairs are con- 

 tinuing to disintegrate. On PL XIX, fig. 15, I have 

 endeavoured to show the appearance of one of the yellow 

 hairs as seen under a high power. The outline is very 

 irregular, and the wall seems to be pierced by minute 

 pores occurring here and there, not on the longitudinal 

 ribs, but between them. I am not really certain of the 

 existence of these pores, but careful examination of sections 

 strongly suggests their presence. On PI. XIX, fig. 16, I 

 have shown one of the granulated hairs as it appears when 

 breaking up. In a section taken near the end of the brush 

 the whole field is strewn with the separated particles. 



The principal peculiarities of the scent-organs in A. whytei 

 are, then, the thin and simpUfied wing-patch, and the central 

 pencil of fine stiff hairs in the brush. 



So far the organs examined have all been taken from 

 species of one genus, viz. Amauris. It will now be profitable 

 to investigate the structure of the scent-apparatus in other 

 Danaine butterfiies. 



As an example of a small but important genus we may 

 take Tirumala petiverana, Doubl. 



In this genus the alar scent-organs do not form a patch, 



