162 f-^"i-T' 



On May lltli largest specimen 21 mm. long, but is not fully 

 sti'etclied, so might easily be 22 mm. 



The full-grown larva, unlike the practically colourless state of 

 previous instars, is so only beneath, but above has the back darkish olive- 

 green, the lower margin being a very straight line, immediately below, 

 but touching which are the minute dark oehreovis spiracles. Seen 

 laterall}^ the bright white line of the lateral tracheal trunk is con- 

 spicuous, but is invisible from above, being hidden by the coloured dorsal 

 skin. The head is black, but with mouth-parts pale, and there is a pale 

 transverse area above the mouth-pai'ts but below the e3^es. This varies 

 a good deal in different specimens ; when it reaches above the eyes these 

 show quite black. Each segment has dorsally 7 subsegments, of which 1st 

 and 6th are narrow, 7th much the largest. The prothorax is whitish 

 except the last subsegment, which is greenish, and there is some whitish 

 in front of mesothorax. The abdominal segments 2, 3, 4, 5, 6, 7, 8, and 

 10 have pro-legs, 1 and 9 are without, but have the same dorsal structure 

 and colour as the others. The 10th is not subsegmented, and looks very 

 smooth. It seems, in fact, to be covered by a very large anal plate. 

 This carries on each side at its anterior margin a large black mark that is 

 not seen in previous instars. 



The hairs are much as in previous instars, but decidedly less numerous 

 across the dorsum and of a length of about 0*04 mm., very numerous at 

 posterior end, where not a few are O'l ram. long. The anal plate carries a 

 few very small hairs, but the abundant hairs are just behind it. The 

 pro-legs have numerous hairs about 0'06 mm. long. Hairs are not 

 abundant near the spiracles. 



The cast skins exhibit very easily the structure of the mouth-parts: — 

 The six- jointed antennae, the four-jointed maxillary palpi, the tliree- join ted 

 labial palpi, the rows of stiff bristles on the labrum, the large, strong, 

 ?coop-shaped jaws with seven teeth around the margin of the scoop, each 

 tooth with finely-serrated margin. 



It may be noted that in moulting they have the common sawfly 

 habit of fixing the effete skin by some glutinous material applied at the 

 posterior end, so that it remains fixed whilst (and after) the larva 

 escapes from it. In Le])idoptera we are familiar with the use for this 

 object of the crochets of pro-legs and a silken carpet. 



Ueigate. 



June 1920. 



