402 



NEUROPTERA 



CHAP. 



of branchiae during the aerial life have been the source of some 

 perplexity ; the condition was shown to exist 

 in Pteronarcys by Newport, and has since 

 been demonstrated in various other forms. 

 IsTewport believed that the imago of Ptero- 

 narcys breathes by means of the gills, 

 although it lives out of the water and 

 possesses spiracles ; and he informs us that 

 Mr. Barnston observed the Insect when on 

 the wing " constantly dipping on the surface 

 of the water." Hence Newport concluded 

 that Pteronarcys in the winged state is " an 

 amphibious animal." That a winged Insect 

 should live in the air and yet breathe by 

 means of gills would be truly extraordinary, 

 and there can be little doubt that Newport's 

 idea was erroneous. Hagen -^ was able to 



Fig. 254. Under side of examine living imagos of the species in ques- 



body of Pteronarcys . o ^ ^ - i i 



regaiis, imago. (After tion. He found that they avoided the 

 Newport.) g, Tra- ^y^ter, and though he placed some indi- 



cneal gills ; o, sternal ^ ' ^ ^ ^ ^ 



oritices. viduals therein, yet they did not use the 



gills. He also informs us that the branchiae 

 have, during life, a shrivelled appearance, indicating that they 

 are not functionally active, but are merely useless organs carried 

 over to the imago from the previous instar, in which they were 

 truly the means of obtaining air. Hagen also ascertained that 

 the spiracles of the imago are in a normal state, being adapted 

 for breathing, even as far back as the seventh abdominal 

 segment. 



Great difference of opinion has prevailed as to the relations 

 of the branchiae to the stigmata, it having been contended that 

 the falling off of some of the branchiae left the stigmatic orifices. 

 The facts appear to be only consistent with the conclusion that 

 the two are totally independent organs. This subject has been 

 investigated by Palnien,^ who finds that in Perlidae contrary 

 to what occurs in may-flies the species are either entirely 

 destitute of gills, or these organs are persistent throughout 

 life. It is not to be inferred from this that the gills in. the 



^ Stettin, ent. Zcit. xxxviii. 1877, p. 487. 

 - Morphologie des Tracheeitsy stems, Helsingfors, 1877, p. 21. 



