202 NATURAL HISTORY OF AQUATIC INSECTS CH. 



Eristalis larva : " The tail is divisible into three 

 sections. There is an outer sheath, immediately 



FIG. 71. Diagrams of tail of larva of Eristalis larva; i. fully extended ; 5, com- 

 pletely retracted ; rt, respiratory tube ; chs, channelled sheath ; 7t'i, wrinkled 

 sheath ; ^, body of larva. In 3 and 4 the retractor muscles are shown ; 6 shows 

 the tracheae within the respiratory tube and channelled sheath (J. J. Wilkinson). 



continuous with the integument of the body ; an 

 intermediate sheath, marked by about forty longi- 

 tudinal furrows, and hence called 'the channelled 



