2 T o Studies in the Theory of Descent. 



no spot, and here no ring-spot is afterwards 

 formed. Besides these markings, there was only 

 to be seen a yellowish-white spiracular line. 



This solitary specimen unfortunately buried itself 

 before the moult for which it had prepared itself 

 had occurred ; but this ecdysis is associated with 

 a very important transformation. This statement 

 is founded on a blown specimen in Staudinger's 

 collection ; it is only 18 millimeters in length, 

 but already shows the later grey colouring in 

 place of the beautiful green. In this, the third 

 stage, the broad white subdorsal line bears on 

 each segment a red spot enclosed between black 

 crescents above and below (Fig. 49 A). In the 

 fourth stage, during which I have seen many 

 living caterpillars, the subdorsal line is still dis- 

 tinctly present in some individuals (Fig. 14), but 

 the spots (" mirrors ") are now completely sur- 

 rounded by a narrow black ring (" ground-area "), 

 which sharply separates them from the sub- 

 dorsal line (Fig. 49 B). In the fifth stage this 

 ring becomes a somewhat irregularly formed black 

 " ground-area," whilst the subdorsal line com- 

 pletely vanishes (Figs. 51 and 49 C). The mirrors 

 are white, but generally have a reddish nucleus, 

 which obviously corresponds to the primary yellow 

 spots from which the whole development of the 

 ring-spots originates. This character is, however, 

 sometimes absent ; and many other variations also 

 occur in the earlier stages, all of which can be 



