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TEXT-BOOK OF ENTOMOLOGY 



Dewitz found that young nymphs of Ephemerids will well endure the ampu- 

 tation of their gills, while fully grown ones die. Amputation of the lateral gills 

 hastens ecdysis. After the change of skin, the gills are smaller than before, and 

 at first contain no tracheae, but in a few weeks they develop as completely as in 

 normal individuals. The caudal gills were also renewed. 



In the nymphs of Perlidae the tracheal gills are usually present, 

 and are either foliaceous (Nemoura) or more commonly filamentous 

 in shape (Fig. 442). They are situated either on the prosternum 



(Nernoura and Pteronarcys), or on each 

 side of the thorax, or on the sides of 

 the abdomen, or are restricted to a 

 tuft on each side of the anus at the 

 base of the caudal stylets (Pteronarcys 

 and Perla). Unlike the Ephemeridae 

 the gills persist in certain genera 

 throughout life. 



The larvae of the aquatic Neurop- 

 tera, Sisyra, Siaiis, and Corydalus 



possess lateral 

 pointed bristle- 

 like tracheal 

 gills, which in 

 Sisyra are 2- 

 jointed ; those of 

 Sialis are, in the 

 living larva, 

 curved upwards 

 and backwards 

 (Fig. 444). Cory- 

 dalus is also provided with a ventral tuft of delicate filamentous 

 gills, which, however, according to Riley, do not appear until after 

 the first moult. 



While the nymphs of Agrionidse (which have rectal gills) respire 

 chiefly by the large caudal foliaceous gills (Fig. 445), there are, 

 according to Hagen, two genera of the Calopteryginse (Euphaea, Fig. 

 446, and Anisopleura) whose nymphs possess seven pairs of external 

 lateral tracheal gills, in shape like those of Sialis, besides three caudal 

 and three rectal tracheal gills. 1 



1 Mr. J. W. Folsom, who has made the accompanying sketch of the nymph of Euphsea 

 splemlais in the Cambridge Museum, finds only seven pairs of gills, there being no 

 traces of them on segments 1, ( .i, and 10. A stout trachea, he writes us, enters the 

 base of each gill, and subdivides into several long branches, which course along the 

 periphery. Hagen in his original account said there were eight pairs on segments 

 1-8 respectively. 



FIG. 443. A, larva of Sisyra, enlarged. S, one of the hinder pills, 

 with its tracht-ii-. After Westwood, from Sharp. C, a gill, showing 

 the branched trache;e. After Grube. 



