236 St^tdies in the Theory of Descent. 



velopment the red spots become more strongly 

 pronounced. Among eighty caterpillars from one 

 brood there were about twenty without any red 

 whilst the remainder were ornamented with more 

 or less vivid blood-red spots, often large and irre- 

 gular in form. In some specimens the spots had 

 become drawn out into lines, 29 forming a coloured 

 edge to the oblique white stripes, similar to that 

 possessed by the larva of Sphinx Ligustri. The 

 caterpillar is thus represented in many figures, but 

 generally the coloured stripe is made too regular, 

 as in reality it is always irregularly defined above, 

 and never so sharp and even as in Sphinx 

 Ligustri. The character is here obviously not yet 

 perfected, but is still in a state of development. 



SMERINTHUS POPULI, LINN. 



From green spherical eggs there emerged larvae 

 6.5 millimeters in length without any markings. 

 They were of a light greenish-white, the large head 

 and long caudal horn being of the same colour. 

 The posterior boundary of the segments appears 

 as a light shining ring (PL VI. Fig. 55). 



The characteristic markings of the genus appear 

 on the following day without the occurrence of any 

 moult : seven oblique white stripes arise from near 

 the dorsal line, and extend along the sides in a 

 direction parallel to that of the horn. On the 

 three front segments they are represented only by 

 * J The caterpillar is thus figured by Rosel. 



