The Origin of the Markings of Caterpillars. 24 i 



horn, these changing to bluish. Specimens occur, 

 although but rarely, which show in this last stage 

 red spots in the vicinity of the oblique stripes, just 

 in the same manner as with Populi> in which 

 species, however, they occur more commonly. I 

 only once found an adult larva of Ocellatus 

 possessing reddish-brown spots above and below 

 the oblique stripes, 30 exactly as in one of the 

 specimens figured by Rosel/ 



31 



80 [In 1879 Mr. E. Boscher found about thirty full-grown 

 caterpillars of this species in the neighbourhood of Twickenham, 

 ten to twelve of which were feeding on Salix viminalis, and 

 the remainder, from a locality not far distant, on Salix triandra. 

 The whole of the specimens taken on the plant first named, 

 had the red-brown spots above and below the oblique stripes 

 more or less completely developed, as I myself had an oppor- 

 tunity of observing. In these spotted specimens the ground- 

 colour was bright yellowish-green, and in the others this 

 colour was dull whitish-green above, passing into bluish-green 

 below. Should these observations receive wider confirmation, 

 it would be fair to conclude that this species is now in two 

 states of phyletic development, the more advanced stage being 

 represented by the brighter spotted variety. (See also Proc. 

 Ent. Soc. 1879, P- xliv.). Mr. Peter Cameron has recently 

 suggested (Trans. Ent Soc. 1880, p. 69) that the reddish- 

 brown spots on the Smerinthus caterpillars may serve for pur- 

 poses of disguise, as they closely resemble, both in colour 

 and form, certain galls (Phytoptus) of the food-plants of these 

 species. If this view be admitted, these spots must be 

 considered as a new character, now being developed by 

 natural selection. The variation in the ground-colour of the 

 two forms of S. Ocellatus may possibly be phytophagic, but 

 this can only be decisively settled by a< series of carefully con- 

 ducted experiments. R. M.] 



31 " Insekten-Belustigungen," Suppl. PL 38, Fig. 40. 



R 



