96 Larval and Pupal Starjes of Bibio Johaniiis L. 



width than length. The larva is clearly divided into two distinct 

 regions, (i) The Head and (ii) The Body. 



The Head is very clearly defined and is invested by a shining chestnut- 

 brown chitinous capsule which is darker and stronger than the covering 

 of the body. The head can be slightly retracted, so that the posterior 

 end is covered by the front of the first segment of the body. It is darker 

 in the anterior half and on that half bears a few long single setae, while 

 the posterior half, which is lighter, is bare. From the centre of the hind 

 edge of the head arises a fine dark line which passes forwards and almost 

 immediately divides into two, which curve outwards to the bases of the 

 mandibles (Plate II, fig. 5). 



The paired appendages of the head are the antennae, mandibles and 

 the first maxillae. Between and below the maxillae there lies a rather 

 peculiar shaped plate. This structure probably represents the second 

 maxillae fused to form a single organ. This plate has another rather 

 crescent shaped plate lying above it. A similar structure often occurs 

 in Dipterous larvae. The lower plate is regarded by Miall and Ham- 

 mond (17) as the sub-mentum, while the upper plate is regarded as the 

 mentum, which, they consider, has gradually slipped behind the sub- 

 mentum. 



The sub-mentum is dark and strongly chitinised, with a central 

 lighter area bearing a group of short setae (Text-fig. 7, p. 112). 



There does not appear to be any indication of eyes, and the antennae 

 (Text-fig. 6, p. 1 12) are small and inconspicuous. The mandibles 

 (Text-fig. 4, p. Ill) are large, strong and dark, and have each two large 

 teeth and two smaller ones. They bear on their inner side a prominent 

 group of fine setae some of which are slightly branched. 



The maxillae (Text-fig. 5, p. HI) are stout and have a distinct 

 palp. The tops of both palp and maxilla bear a number of setae. 



The Body is nearly cylindrical, but is slightly flattened dorso-ventrally 

 and normally is curved slightly, the ventral surface forming the inside 

 of the curve. The body consists of twelve segments, of which the first 

 is the longest and has rather the appearance of two segments, but the 

 imaginal discs prove it to be a single segment. 



The body bears ten pairs of spiracles which are brown in colour and 

 are situated, a pair on each segment, on all segments except the second 

 and eleventh. The spiracles are situated laterally except those on the 

 twelfth segment which are placed more dorsally than the others. The 

 spiracle on the first segment (Text-fig. 1, p. 110) is about twice the size 

 of those on the third to tenth segments, and that on the twelfth segment 



