522 Mr. C. L. Withycombe's Notes on 



Descripion of Full-fed Larva. (Plate XXXVIII, fig. 2.) 



Length about 5 min. Hairy, and somewhat oval in shape when 

 resting. Colour pale olive green or brownish, the gut contents 

 showing through in the mid-body, rosy or orange. 



The head is small and rounded, pale in colour. Projecting 

 laterally are the black eyes, each composed of six ocelli. Antennae 

 are fifteen- to sixteen-jointed, long and slender. The thirteenth 

 joint bear.s a long bristle externally. The fourteenth is rather 

 spindle-shaped and more blackish than the rest. The terminal 

 joints are small. The jaws are extremely long and slender, composed 

 of closely applied mandibles and maxillae as usual. They are very 

 flexible and in life can be curled up or down, especially at the apices, 

 reminding one in their movements of the proboscis of a Lepido- 

 pteron, though, of coiirse, not quite so flexible as this. As gcneraUy 

 carried, however, they are almost straight, curved at the tips 

 slightly outwards and downwards. Labial palpi are entirely absent. 

 The body is provided dorsally with a complete chitinous tergum 

 per segment. These dorsal shields are of a brownish colour, with a 

 pale median line running through each. Latero-dorsally there is a 

 pair of bristle tufts per segment, each arising from a v/art-like 

 projection, and having two or three lighter spots on the chitin 

 round it. There is also one prominence, bearing a tuft of setae, on 

 each side of all the segments. On the 8th abdominal segment the 

 prominences and bristles are considerably longer. The lOth 

 abdominal segment, or anal papilla has a pair of eversible appen- 

 dages, but these are rarely used. Ventrally the body is paler in 

 colour and soft, but with several sclerites in the thoracic region. 

 The legs are remarkable in that there is only one tarsal claw. From 

 each of the first seven abdominal segments, ventral to the spiracles, 

 arises a pair of jointed, leg-like tracheal gills, each with two tracheae. 

 These lie near the venter, but not touching it. The first gill is 

 largest, but only tv/o-jointed and with a recurrent projection near 

 its base. The succeeding appendages are three-jointed and the 

 projection is progressively less marked on each, from second to last. 

 In life these gills are kept in exceedingly rapid vibration, so that 

 the ventral side of the body appears hazy below. This vibration is 

 far more rapid than ' in the gills of Cloiion larva, for instance. 

 Intermittently vibration ceases. 



I think we may safely say that the larva of Sisyra has 

 been derived from an earlier form with shorter jaws, as in 

 Osm.jjlus. This suggestion is supported by the fact that 

 the young Sisyra has short and rigid jaws. I must confess 



