298 Dr. T. A. Chapman's Contribution to 



become faintly rufous. The Hght aspect of the larva is 

 assisted by the greater abundance of medium-sized hairs 

 as will be seen in PI. XLVI. (PI. XXVI, fig. 12, and PI. 

 XXVII.) 



Mr. Main's photographs of the larvae and pupae of 

 A. thersites and P. icarus are very instructive in some 

 points, and so I present them. They are in several 

 instances stereoscopic, and the figures are placed close 

 enough to be easily combined without the aid of a stereo- 

 scope. They are all X 2. 



They bring out very distinctly the much brighter appear- 

 ance of A. thersites (larva) owing to the absence of dark 

 hairs on the abdominal segments and the greater abundance 

 of the larger secondary hairs. The pupae of the two 

 species are very much alike, the larger size of the icarus 

 pupa shown is an individual not a specific difference. 



When first moulted into last instar P. icarus has white 

 hairs except on thorax (like thersites mature plumage), 

 but in a few hours, some 7 or 8 hairs on either side of each 

 segment on the dorsal ridge become black, and most of the 

 long hairs on the lateral flange become nearly black, often 

 in both cases remaining pale close to the body. The pale 

 spiracles are more conspicuous, and the yellow dorsal and 

 lateral lines are barely to be detected. (PI. XXVI, figs. 

 5 and 6.) 



The photographs of the honey-gland region of thersites 

 and icarus, PI. XLVI, are from specimens that agree with 

 several others of each species in showing certain differences 

 that may be taken to be constant in the last instar. 



In thersites on the dorsum of 6th abdominal segment are 

 5 long hairs on each side, in icarus at least twice as many, 

 on 7th icarus has two strong hairs above spiracle that are 

 wanting in thersites, which also has none on dorsum of 8th 

 where icarus has a pair. On the other hand, icarus has a 

 very moderate supply on these segments of medium and 

 small hairs, compared with their abundance in thersites. 



The photographs of dorsal hairs (PI. XXII) are difficult 

 to compare, for it so happens that the skin of icarus is 

 spread or stretched nearly twice as much as that of thersites ; 

 so that only the posterior half of the segment is shown of 

 icarus, the whole width of the segment in thersites. 



They show, however, that the long hairs of icarus are 

 longer than those of thersites (about 0"6 mm. to 0'48 mm.), 

 that smaller hairs are much more abundant in thersites, 



