96 The Colours of A nimals. 



wave in the upper line. After another five or six 

 days, and when about half an inch in length, our 

 caterpillars moult again. In their third stage (fig. 

 17), the commencement of the eye-spots is more 

 marked, while, on the contrary, the lower longitu- 

 dinal line has disappeared. After another moult 

 (fig. 1 8), the eye-spots are still more distinct, the 

 white gradually becomes surrounded by a black 

 line, while irt the next stage (fig. 19) the centre 

 becomes somewhat violet. The white lines have 

 almost or entirely disappeared, and in some speci- 

 mens faint diagonal lines make their appearance. 

 Some few assume a brownish tint, but not many. 

 A fourth moult takes place in seven or eight days, 

 and when the caterpillars are about an inch and a 

 half in length. Now, the difference shows itself 

 still more between the two varieties, some remain- 

 ing green, while the majority become brown. The 

 eye-spots are more marked, and the pupil more 

 distinct, the diagonal lines plainer, while the white 

 line is only indicated on the first three, and on the 

 eleventh segment. The last stage (fig. 19) has been 

 already described. 



4. Now, the principal points to which I wish to 

 draw attention are (i) the green colour, (2) the 

 longitudinal lines, (3) the diagonal lines, (4) the 

 brown colour, and (5) the eye-spots. 



As regards the first three, however, I think I 

 need say no more. The value of the green colour 

 to the young larva is obvious ; nor is it much less 



