The Origin of the Markings of Caterpillars. 265 



I have frequently succeeded in obtaining fertile 

 eggs of Anceryx Pinastri and I will now give the 

 developmental history of this caterpillar, which has 

 already been figured with great accuracy in Ratze- 

 burg's excellent work on forest insects. Rosel 

 was acquainted with the fact that the " pine moth" 

 laid its eggs singly on the needles of the pine in 

 June and July, and he described them as " yellow- 

 ish, shining, oval, and of the size of a millet seed." 



On emerging, the caterpillars are six millimeters 

 in length, of a light yellow colour, the head shining 

 black with a yellow clypeus. The caudal horn, 

 which is forked at the tip, is also at first yellowish, 

 but soon becomes black. No particular marking 

 is as yet present, but a reddish stripe extends 

 along the region of the dorsal vessel, and the 

 course of the spiracles is also marked by an orange- 

 red line. (Fig. 53, A & B, PL VI.) 



As soon as the young larvae are filled with food 

 they acquire a greenish streak. The first moult 

 occurs after four days, and immediately after this 

 there is still an absence of distinct markings, with 

 the exception of a greenish-white spiracular line. 

 In the course of some hours, however, the original 

 light green ground-colour becomes darker, and at 

 the same time a sharp, greenish-white subdorsal 

 line appears, together with a parallel line extend- 

 ing above the spiracles, which, in Pterogon Gor- 

 goniades, has already been designated as the 

 " supra-spiracular." The dorsal line is absent : 



