90 



The Fly of Chironomiis 



Fig. 6o. — Details of imaginal head, i, dis- 

 section to show the chitinous tunnels 

 (cc) behind tlie epistome. 2, posterior end 

 of one of tlie tunnels, with slit-like opening. 

 3, extremity of labium. 4, extremity of 

 ling^ua. 5, one of the processes on the 

 vertex. 



antennae. In many in- 

 sects there occurs in a 

 somewliat similar situa- 

 tion a tentorium, or in- 

 ternal skeleton for mus- 

 cular attachment, which 

 splits into halves at each 

 ecdysis, and, according to 

 Palmen's observations on 

 Ephemera, is renewed 

 from paired rudiments. 

 Other writers ^ have traced 

 the tentorium to the spira- 

 cles of the jaw-bearing 

 segments. These ideiiti- 

 fications are still doubt- 

 ful. Very similar hollow 

 processes for muscular 



Fia. 61. — Section of imaginal head. &, enlarged second joint of antenna, 

 f, chitinous tunnel, e, epistome. I, labella. 



1 CarriiTe on Ohalicodonia. 1897 ; Wheeler on Doryphora, 1889. 



