142 



The Pupa of Chironomus 



boundary between the pro- and mesothorax. The tra- 

 cheal gill was clearly seen in front of the line, while the 



Fig. 108. — Dorsal views of the thorax of a late larva, showing the 

 position of the paired bases of tlie tracheal gills of the pupa just in 

 front of the strong transverse line that separates the pro- from the 

 mesothoiax. In tlie right figure the larval skin has been removed, 

 except from the head, so that the wings are suffered to expand. 

 The prothorax here has suffered some degree of contraction. 



anterior or mesothoracic spiracle of the imago lies in the 

 line. 



The tracheal gill branches primarily into a larger 

 anterior lobe and two posterior bifid lobes. These again 

 1 



F16. 109. — I, tracheal gill of pupa and adjoining fore-leg in side view, 

 as seen through larval skin. 2, filaments of tracheal gill, x 350. 



become divided into numerous long filaments, which float 

 freely in the water (Plate, figs. 5, 6). A stiff cylindrical 



