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 ; ;■/, respiratory' tube ; chs, channelled sheath ; ws, wrinkled 

 sheath ; b, 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 b\- about fort}- longi- 

 tudinal furrows, and hence called 'the channelled 



