Vol. XXvi] ENTOMOLOGICAL NEWS. 437 



for the nymphs live after the removal of the processes 



[and] the skin of these processes is harder than is usual 

 in Insect gills." Similar views were also expressed by Hey- 

 mons (1904, pp. 23, 24) : 



The exchange of gas during this period [youngest larval stages] is 

 accomplished without doubt not solely through the appendages, but in 

 a sufficient way through the entire body-surface which at first is cov- 

 ered with extremely delicate chitin. .. .During the larval period there 

 can be no doubt that the three appendages have become primarily 

 breathing organs from the physiological standpoint. But, as earlier, 

 the entire body-surface serves for respiration in addition to the gill- 

 appendages and a loss of the appendages in no way leads to death of 

 the animal. 



Tillyard (1909, pp. 381-2), discussing the caudal appen- 

 dages of the larva of the Australian Diplilebia, while admitting 

 that "the presence of numerous branched tracheae in these 

 gills" must mean "that orig'mall\ they were in some way or- 

 gans of respiration," points out that the loss of these gills 

 "does not affect the respiration of the insect in any way," and 

 doubts "whether even the wide lateral gills of Diphlebia, fed 

 by two large tracheae, are of any use at present for auxiliary 

 respiration." 



RECTAL RESPIRATION. CALOPTERYGINAE. 



The earliest record of observations on rectal respiration in 

 this group appears to be that of Roesel von Rosenhof (1749, 

 p. 43) when he says of the nymphs [of Caloptcry.v} that they 

 draw "their air not through the mouth, but through the abdo- 

 men, and such can easily be perceived in them if they are kept 

 in a clear glass full of water." Dufour (1852,- p. 91) saw 

 larvae of Caloptcrix "swallow through the anus the water 

 which serves for their respiration." He described (1849, 1852, 

 p. 87) gills in the rectum as forming three membranous folds 

 ("raquettes") fixed by a single extremity to the inner and 

 posterior part of the stercoral pocket in such manner as to be 

 free and floating for two-thirds of their length. Hagen (18800, 

 p. 1 60) found these gills "genau wie Leon Dufour." This 

 statement was called forth by Olga Poleta'iew's denial (1880, p. 

 450) of the existence of rectal gills in the larva of Calopteryx 



