146 The Pupa of Chironomus 



of tlie cuticle- secreting epidermis, resumes its activity. 

 The cells multiply and enlarge, form a layer over the 

 scar, and secrete new cuticle. In a few hours the only 

 external indication of the place where a tracheal gill 

 once projected is an oval scar, which is easily seen on 

 the thorax of the fly (fig. 72). 



We have already remarked (p. 10) that there is 

 a section of Chironomus (the motitator group of Meinert) 

 in which the pupa is provided, not with bunches of 

 » filaments, but with a pair of trumpets. 



Papal Sedentary aquatic pupae, which are unable to come 



fr^^n^oT'^ to the surface of the water, may be provided with 

 other branched and filamentous gills like those of Chironomus 



Nemoccra. (^plumoisus sectiou) or Simulium. Free aquatic pupae are 

 able to float at the surface without effort, and are com- 

 monly provided with respiratory trumpets, whose tips 

 just reach the surface of the water when the pupa is at 

 rest. The trumpets, instead of a single orifice, may have 

 a row of small holes ; in particular cases the passage is 

 closed by a thin membrane. The respiratory trumpet of 

 the pupae of Culex, Corethra, certain species of Chiro- 

 nomus, &c., is perhaps the equivalent of the common stem 

 of the pupal tracheal gill of Chironomus dorsalis, &c. 

 The numerous holes in which the trumpet of the Dicra- 

 nota-puj)a ends may perhaj^s correspond to the short 

 tubes which in Chironomus dorsalis lead from the 

 tracheal trunk to the tracheal gill of the pupa (see p. 144). 

 The pupal trumpets are very long and slender in some 

 species of Limnophila ; one of the pair is longer than the 

 body in Ptychoptera and Bittacomorpha. In Ptycho23tera 

 they exhibit a very peculiar and interesting structured 



Provision On the dorsal surface of the pupal thorax an inter- 

 ^or^e^cape ^^.^^^^^^ median white line may be seen, and on either 

 side of it a curved line of similar character (fig. 112). 

 Along these lines the integument is slightly sunk, and 

 thinner than elsewhere, while the close-set cuticular hairs, 

 so prominent elsewhere, disappear. These hairs are pro- 



' Grobben, 1875 ; Miall, 1895. 



