318 Mr. Poulton's further notes upon the 



extremely unlike the remaining three in ground colour, 

 markings, and shape. The two former are very dark, 

 almost black, with white bands at intervals round the 

 central part of the body, while the larva is cylindrical. 

 The three last stages are very similar to one another, 

 but much more complicated than the first two, and the 

 break very sudden. The chief traces of continuity are 

 seen in the permanence of the anterior white band in a 

 modified form, and in the changes that take place 

 towards the end of the second stage. These latter, 

 however, are probably due in a great measure to the 

 actual existence of the third stage beneath the tightening 

 skin of the second. The last three stages bring out the 

 importance of attitude in a very interesting way. With 

 a similar colouring and structure the appearance of a 

 larva in the third stage at rest is extremely different 

 from one in the fourth or fifth stage, and the difference 

 is correlated with a position upon leaves or branches 

 respectively. It is very likely that some such difference will 

 be found in the ontogeny of all Geometer larvse which are 

 protected in the advanced stages by resembling twigs. 

 The rhythmical lateral movements are very hard to ex- 

 plain. The habit seems to be extremely ancient, as it is 

 so widespread and so frequently manifested. At present 

 I can only suggest a possible use in the unvarying and 

 mechanical characters of the movements which are cer- 

 tainly very unlike those generally seen in organic forms. 



14. The utilisation of the changes in colour before 

 PUPATION FOR PROTECTIVE PURPOSES. — In a paper read 

 before this Society last year (November 7th, 1883), I 

 suggested that the darkening of certain larvae before 

 pupation is probably of protective value. I was not 

 then aware that this suggestion had been previously 

 made by Mr. Meldola (see his paper in Proc. Zool. Soc, 

 1873, p. 155, and the Appendix to his translation of 

 Weismann's book quoted above, p. 525). Mr. Meldola 

 instances the darkening of Sphinx ligastri, and this was 

 the very larva which prompted me to make an identical 

 suggestion, quite independently, although many years 

 afterwards. In my last paper I gave instances of green 

 larva; protected by their resemblance to leaves, which 

 became brown when they wandered over the bare ground 

 before burying, and other larvse which darkened less, 

 still retaining green as their predominating colour, and 



