286 Mr. Poulton's notes in 1886 



only present in extreme varieties. Furthermore, in 

 S. tilice the red band or spot was remarkably small 

 upon this segment. Hence it is probable that S. popuK 

 is abnormal in this respect. The larvae here described 

 probably indicate that the spots in the larva already 

 referred to, as figured by Mr. Bignell, are represented 

 as too numerous in the anterior part of the body, for in 

 neither of these extreme varieties did the number of spots 

 in any row ever exceed the number of the segments. 



The spiracular row of spots was well marked in these 

 lame, and a small spot appeared on the third thoracic 

 segment and a larger one upon the second in the 

 yellowish larva ; the latter spot being well developed in 

 the whitish larva, but the former and that around the 

 prothoracic spiracle could not be seen when the larva 

 was examined (perhaps because it was examined some- 

 what late, after the changes of colour before pupation 

 had commenced). 



The claspers were all marked, but this row was not 

 well developed, the spot on the anal clasper of the 

 yellowish larva being especially small. 



A character, new to me, was the extension of the 

 system on to the head. The head of the yellowish 

 variety is represented from the left side in Plate X., 

 fig. 2, x 2 diameters. The chief colour is on the area 

 of the ocelli, and it extends over the marginal line as a 

 linear vertical mark on the face. The apex is also 

 suffused, the colour extending on to the sides of the 

 upper part of the face. The red tint formed the ground 

 colour, for there were no red apical tubercles. The 

 whitish larva possessed the ocellar and apical red areas, 

 but not the extension of the former. 



On July 6th I had the opportunity of examining a 

 number of larvae, reared by Mr. Arthur Sidgwick from a 

 single batch of eggs, and all fed under the same con- 

 ditions of light, and with the same food — Populus nigra 

 and balsam poplar. The colours and development of 

 spots is seen to be very heterogeneous. 



