marHntjs and attitudes of lepidoptcrnm larrm. 309 



the suggestion that there is no significance in the red 

 spots occiuTing only upon the yellowish variety of 

 S. ocellatiis. 



A more detailed account of the experiments upon 

 *S'. ocellatm and *S'. I'Kjmtn, together with a consideration 

 of the difficulties attending the interpretation of many 

 facts by a theory of " phytophagic " coloration, and an 

 account of the structural basis of colour in larvae and 

 its dependence upon the food-plant, will be found in my 

 paper, " On the essential nature of the colouring of 

 phytophagous larvae," &c., Proc. Koy. Soc, vol. xxxviii., 

 No. 237, pp. 269—315. 



13. The ontogeny op the larva of Selenia illunaria. 

 —The eggs were laid (April 4th and 5th, 1884) by 

 a captured female of the spring brood, and were kindly 

 sent to me a few days later by Mr. W. Holland, of 

 Keading. They are oval, 1 mm. in their longer, and 

 •75 mm. in their shorter diameter, and a little flattened 

 from above downwards. The eggs were all red-brown in 

 colour when they reached me, but subsequent observa- 

 tions upon the later brood showed that they are first 

 light yellow, and that they darken to red-brown in two 

 or at most three days after being laid. Just before 

 hatching the eggs again change colour, becoming very 

 dark grey, almost black. This darkening is generally 

 complete in one day, but it takes place more rapidly in 

 the ova which hatch latest. The larvae emerge in from 

 one to three days after the last darkening is complete. 

 The larvae first appeared May 2nd, and all had emerged 

 by May 11th, but a large proportion of the ova (23 out 

 of 57) were hatched on the first two days of this period, 

 while the rest of the eggs gradually hatched on the 

 remaining days. 



The chief object in working out this ontogeny was to 

 test further the theory I suggested last year (after work 

 on the EphfjrkUe) that young Geometer larvte assume 

 attitudes conducing towards protection during rest upon 

 the surface of leaves, which will, of course, be very 

 different to the well-known positions taken up in later 

 life, when the larvae cling to branches of the food-plant. 



Stage^ I.— The young larvae (fig. 15, x 6, Plate VII.), 

 when first hatched, are about 2*75 mm. long when 

 extended, and are rather stout. They have the habit 

 (very common among Geometer larvae) of moving the 



