H. M. Morris 93 



3. MORPHOLOGY OF THE LARVA. 

 (a) Newly hatched laeva. 



The eggs hatched under laboratory conditions in forty-eight days, 

 on May 30th, which appears to be an exceptionally long period. The 

 newly hatched larva is from 1-3 to 1-5 mm. in total length, of which the 

 head measures about -18 mm., with a breadth of -16 to -19 mm. The 

 head is relatively large, yellow brown in colour, and bears a number of 

 long setae. 



The body is almost colourless, the contents of the alimentary canal 

 showing through as a broad dark line. In shape it is cylindrical, but it 

 is slightly curved, as in the adult. The body is divided into twelve 

 segments, of which the first is the largest. Each segment bears a number 

 of long slender setae, the length of which varies on different parts of the 

 segment. 



Between the long setae on each segment are a number of smaller 

 projections on the cuticle, which correspond to the scale-like structures 

 of older larvae. These projections each consist of a blunt conical base, 

 bearing a single pointed seta, which is directed obliquely backwards. 

 Of the long setae those on the sides are the longest, except on the last 

 and penultimate segments, on which segments those setae situated 

 dorsally are the longest. Each of the long setae arises from a base 

 similar to, but larger than, those of the small setae (Text-fig. 11, p. 112). 



The young larva bears a single pair of spiracles, which are situated 

 on the last segment in a corresponding position to that occupied by the 

 spiracles of this segment in the fully grown larva. At the present stage 

 each spiracle has only a single opening. 



The structure of the spiracles is similar to that of the spiracles on 

 segments three to ten of the adult larva, but they project very little 

 from the body. 



From the extremity of the last segment the larva is able to protrude 

 a pair of membranous conical structures, one on either side of the anus. 

 These structures are protruded by blood pressure, and withdrawn by 

 means of special muscles attached to them. They assist the larva in its 

 movements in a similar manner to the pseudopodia of other larvae. 



The head at this stage is very similar to that of the full-grown larva. 

 The antennae, maxillae and labrum show very slight differences from 

 the adult form. The mandibles are shorter at this stage, and their teeth 

 are relatively longer. The groups of setae on the mandibles are present, 



7—2 



