160 Mr. Poulton's notes in 1885 upon 



minal segment, and it is everted when the larva rolls up 

 on being disturbed. The larval surface close to the lips 

 of the aperture seems to be extremely sensitive to tactile 

 impressions. 



10. The production of a twig-like appearance in 

 THE LARVA OF Hemithea thymiaria. — There are many 

 ways in which the twig-like appearance of Geometer 

 larvae is perfected. In the majority the forward-bent 

 notched head gives a very twig-like termination to the 

 body, but in Selcnia illunarin (see my last paper in 

 Trans. Ent. Soc. Lond., 1885, Part II., August, p. 309, 

 et seq., and fig. 18, PI. VII.) the head is unnotched and 

 bent backwards, producing, with the third pair of 

 thoracic legs placed upon a projecting ridge, a very 

 unlarva-like effect, but one which is easily mistaken 

 for some eccentricity of vegetal growth. On the other 

 hand, the larva of H. thymiaria produces an exceedingly 

 perfect resemblance to a twig by a further elaboration of 

 the more normal attitude. The head is notched and 

 bent forward so that the notches become terminal, but 

 the prothorax also possesses a pair of dorsal tubercles, 

 and, as this segment is rotated forwards and down- 

 wards in the vertical plane, in the protective attitude, 

 the tubercles become also terminal, and are about equal 

 in size to those formed on the head by the notched 

 crown. Thus there is produced an exceedingly regular 

 quadrifid termination to the anterior end of the body, 

 constituting the most perfect of all the close api^roxi- 

 mations to vegetable structures which I have yet seen 

 among Geometer larvse. 



11. The darkening of the hairs of the larva of 

 Acronycta leporina before pupation. — During the 

 past summer (1885) I noticed that the long white hairs 

 of this larva become dark, as well as its body, before 

 pupation, when the organism is wandering about to find 

 a place in which to burrow. I then remembered that I 

 had often previously observed the same thing with this 

 larva obtained plentifully upon birch and alder in the 

 New Forest. As the larva wanders over the bark, and 

 subsequently burrows in it, the dark colour is of great 

 protective use, and is another instance of the utilisation 

 of the incidental changes of colour before pupation. 



