Mouth-parts of Fly 



lOI 



insects ; they are iiifold- 

 ings of the integument, 

 which may either remain 

 hollow or become filled 

 with chitinous deposit. In 

 the Chironomus-fly they 

 are hollow. Each gives 

 off from its upper part 

 a pair of hollow, lateral 

 extensions, so that it may 

 be compared to a letter Y. 

 Each segment bears its 

 own ganglion (fig. 71). 

 The prothoracic and meta- 

 thoracic ganglia occupy a 

 large proportion of the 

 length of their respective 

 segments ; the mesotho- 

 racic ganglion is placed 



the posterior portion of the cavity 

 of the thorax to be mesothoracic. 

 At that time I had not the advan- 

 tage of the serial sections prepared 

 for tlie present description of Chiro- 

 nomus. The section from which 

 fig. 74 is taken shows the larval 

 recti ventrales muscles still remain- 

 ing amid the newly forming mus- 

 cles of the imago. The metatho- 

 racic muscles of this series extend 

 forwards to the medifurca, where 

 the mesothoracic muscles begin. 

 This observation shows me that 

 my former view must be materi- 

 ally altered. I now concur in the 

 viewsstatedin thepresent chapter. 



Fig. 72. — Side view of female Chironomus-fly. The prothorax and meta- 

 tliorax are dotted, tg, scar of pupal tracheal gill, sp, mesothoracic spiracle. 

 The metathoracic and abdominal spiracles are also shown. 



