16 POLIA CHI. 



and then the fine lines were whitish. By the 27th the 

 larvae were in their last coats, and presented but little 

 variation in details ; their attitudes were graceful 

 amongst the twigs of sallow and willow, as they bent 

 and elongated themselves when feeding near the 

 extremities of the leaves. 



The full-grown larva is one and five-eighths of an 

 inch in length, very slender in proportion, cylindrical, 

 though tapering a little at each end, the head 

 rounded, and the antennal papillge well developed, the 

 segmental divisions very delicately defined, as well as 

 the intermediate wrinkles, so that the skin appears 

 very smooth and soft. The colour on the head and 

 back is a delicate bluish-green, quite opaque on the 

 back, the dorsal line very thin, a mere pale thread and 

 edged with darker green than the ground-colour ; the 

 subdorsal line is whitish, better defined, and also 

 edged with darker, indeed this line on the thoracic 

 segments is white ; beneath it, as far as the spiracles, 

 the colour is a transparent yellowish, or else a full 

 green, so clear as to show the branchial vessels 

 through it ; this colour deepens gradually below till it 

 terminates in a fine blackish -green line, along the 

 lower edge of which are the white spiracles outlined 

 with black ; a brilliant pure white stripe follows, very 

 broad along the middle segments, and a little attenu- 

 ated at each end, often extending along the side of 

 the head towards the mouth, and ending behind at 

 the extremity of the posterior leg ; all the legs and the 

 belly are rather paler and more yellowish-green than 

 the back ; after the thoracic segments the tubercular 

 dots are ranged in threes on either side of the dorsal 

 line ; they are paler than the ground, and sometimes 

 ringed with a little darker colour. 



The variations seem to be in the depth of the 

 general ground-colour, more or less blueness of the 

 green, and the presence or absence of a small blackish 

 oval ring with whitish centre, or false spiracle on the 

 side of the third and fourth segments. 



