OF THE SAW-FLIES (TENTHREDINIDJE). 125 



those of Trichiosoma lucorum, which I have more care- 

 fully examined) have short bilobed maxillae, not unlike 

 those of many beetles, with a short, thick and nearly 

 conical 4-jointed palpus, arising from the middle of the 

 outer edge of the maxilla, whilst the mentum is short 

 and transverse, with the labial palpi short, thick, conical 

 and four-jointed, very similar to those of the maxillae ; 

 the labium itself is about as long as the palpi, and ap- 

 parently rounded at the tip. The structure of the lower 

 jaws and lip of Lepidopterous larvae is very different to that 

 here described. The instruments by which the full grown 

 larva is enabled to spin the silken material which serves for 

 its cocoon are attached to the lower lip, and consist of a silk 

 secretor and a spinneret ; but silk is produced in these insects 

 in very small quantities, the cocoons are generally hard, 

 entire, or with particles of mould introduced into the meshes 

 of the silk. 



In general, the body of the saw-fly larvae is only of a 

 single colour, some being entirely white, or very pale green, 

 others black, and others darker green, the last being the 

 more usual colour ; others exhibit the appearance of a fine 

 bloom, or are of an opal hue, whilst others have the sides 

 of the body and back ornamented with longitudinal stripes 

 and spots of different colours. It is interesting, however, 

 to observe that certain species of these larvae are subject to 

 variations in their colours ; like caterpillars they change 

 their skins several times, and after the last moult in certain 

 species they are entirely different in their colouring to their 

 previous appearance, so that no one would at first suppose 

 it possible that it was the same animal which was before him 

 previous to and after its change of skin. 



The Tenthredo Scrophularice is an example of this 

 peculiarity. Until nearly full grown, it is of a whitish grey 



