The Origin of the Markings of Caterpillars. 221 



frequent occurrence, five having been found among 

 the twenty-eight. In these the spots diminish 

 anteriorly in size, perfection, and intensity of colour. 

 Still more frequently (in eleven specimens) are the 

 ring-spots or their rudiments restricted to the 

 tenth and ninth segments, the spot on the latter 

 being without exception less developed than that 

 on the former segment. 



An anteriorly progressing formation of ring- 

 spots thus undoubtedly occurs, the spots generally 

 diminishing in perfection very suddenly towards 

 the front segments ; and specimens, such as that 

 represented in Fig. 60, PI. VII., in which traces of 

 ring-spots are to be seen on all the segments 

 from the tenth to the fifth, are of rare occurrence. 



From what elements of marking are these 

 secondary ring-spots resulting from transference 

 developed ? They do not, as in the case of the 

 primary eye-spots of the Cheer ocampincz, originate 

 in the separation of one portion of the subdorsal 

 line, and the subsequent formation of this detached 

 spot into a " mirror ;" but they arise from the for- 

 mation of a nucleus, first one and then two of the 

 shagreen-dots on the subdorsal line acquiring a 

 yellowish or reddish colour (Fig. 61, PL VII., seg- 

 ments 6 and 7). The ground on which these two 

 spots are situated then becomes yellow (Fig. 61, 

 PL VII., segment 8), and a more or less distinct 

 black border, having the forrn of two small crescents, 

 is afterwards formed. At a later period these two 



