436 ENTOMOLOGICAL NEWS. [DeC, '15 



seq.), who termed them "Ruder-Federn" (rudder feathers), 

 say nothing of any respiratory function for them. Without 

 attempting to determine who was the first author to definitely 

 describe them as gills, it is worth recalling that it was in them 

 that Carus (1827) first discovered the circulation of the blood 

 in insects. To these organs he applied the terms "Schwanz- 

 blattchen," "kiemenartigen Blattchen" and "Schwanzkiemen- 

 blattchen" (pp. 9, 14), and he figured one of them on a large 

 scale (Taf. I, f. 4). He termed the species which he studied 

 Agrion puella and although the specific identification is prob- 

 ably not correct, it is evident that he had before him a typical 

 Agrionine.* 



By Dufour (1852, as already quoted), and by Roster (1886, 

 p. 242), the two functions of respiration and of locomotion 

 were accepted without question. Roster went so far as to con- 

 clude that 



a branchial lamella is reproduced when the individual has reached 

 such [a state] that it is not able to accomplish its development with- 

 out these necessary organs and that the presence of one lamella, al- 

 though compelling the insect to a forced rest, suffices to satisfy all 

 the respiratory needs of the organism. The great variability in the 

 dimensions of these insects can find a cause in the defective develop- 

 ment to which a physical imperfection, such as the absence of two 

 respiratory lamellae, gives rise (p. 245). 



The observation that Agrionine larvae can live without their 

 caudal appendages dates back at least to Roesel (1749, p. 50). 

 Hagen (1853, P- 3ii)i Dewitz (1890, p. 504), and Janda 

 (1910a, p. 32, igiob, p. 607) inferred from this survival some 

 sort of rectal respiration. 



Sharp (1895, p. 422) thought that the respiratory function 

 of the caudal appendages "must be of an accessory nature, 



*It may be mentioned here that the second species which Carus 

 studied and figured as "eine kleine Neuropteren-Larvae," "vielleicht 

 zu Semblis, Sialis, od. dergl. gehorig," was also a Zygopterous larva, 

 as von Siebold pointed out (Archiv f. Naturgesch, VII, i Bd., p. 211, 

 1841) that it resembles the larvae of Agrion forcipula [= Lestes 

 sponsa Hansem.] Packard's implication (1898, p. 397) that it was 

 in the larva of Ephemera that Carus made his first observation of 

 circulating blood is incorrect. 



