218 Observations on Pimi)la pomorum 



measures -22 mm. long and -24 mm. broad, the ratio of the length of the 

 head to the total length of the larva being as 1:5-4; in the fully grown 

 larva the ratio is 1 : 8-3. The antennae are equal 

 in size to those of the fully grown larva, and are 

 consequently of a much greater relative size. (2) The ^^ 



dorsal curvature of the body is much less pro- 

 nounced. (3) The labial and maxillary papillae are 



, 1 • 1 1 r • Fig. 1. Papillae from the 



represented m each case by a group of six or seven g^^ ^^^^^^1 side of the 



minute cuticular structures on either side (Text- labium of a young 

 „,,,,.—,,,, , TT larva: highly magnified, 



iig. 1). (4) The body segments are more rounded 



and uniform in character, and the dorsal pseudopodia are not yet formed. 



(5) The trachea] system is incompletely developed, and nine pairs of 



spiracles are present, the minute vestigial second pair not yet being 



evident. 



6. THE FULLY GROWN LARVA. 



When fully grown the larvae vary from whitish, or dull cream colour, 

 to pale brownish white or pink, and measure when alive from 4-5 to 

 5 mm. in length, with an average maximum breadth of 1-25 to 1-5 mm. 

 They are elongate fusiform in shape, narrowing towards the two ex- 

 tremities, and more so at the anal than at the cephalic end. The dorsal 

 surface is more prominently arched than the ventral (Plate XII, fig. 2), 

 and the cuticle is studded with numerous minute conical chitinous 

 papillae. These structures have an average diameter of '004 mm. and 

 give the cuticle, under a low magnification, the appearance of fine 

 shagreen; those on the dorsal region are slightly larger than elsewhere. 

 A few short setae occur and, for the most part, are grouped in the form 

 of a loose circlet around the middle of each segment. A well-defined 

 head is present followed by thirteen sharply demarcated body segments, 

 which are related to one another in length in the following proportions: 

 6-7:6:5-6:6:7:7-8: 8-9 : 8-9 : 7-8 : 6-7 : 5 : 3-4 : 3. Owing to the 

 variable amount of contraction or extension which the segments undergo, 

 these ratios are not capable of more exact determination. The head 

 differs from the remainder of the body in being enclosed in a smooth 

 and slightly thicker chitinous investment ; it is, moreover, usually a little 

 darker in colour. It is about as broad as long, measuring -6 mm. in 

 either direction. On the dorsal aspect, it has two ovoid or somewhat 

 pyriform infuscate markings, which are placed alongside the middle line, 

 parallel with the longitudinal axis. Definite though vestigial antennae 



