THE ORGANS OF RESPIRATION. 169 



clavate leaves fringed at the margin. The larvae of JEschna and Libel- 

 lula breathe through fasciculated branchiae, which lie in the colon. 

 Thither proceed the terminal ends of the four main stems of the 

 tracheae ; they transpierce the membrane of the colon, and hang as thick 

 fasciculi within the cavity of this organ *. As the creature imbibes 

 water by means of it, and thus again rejects it, it helps to assist it in 

 swimming, which, without this auxiliary aid, it would find it difficult to 

 effect, from its deficiency of other swimming leaves. Other larvae swim 

 by means of the branchial leaves, which move with an incessant 

 alternating vibration. 



Among the Neuroptera we are acquainted with the families of the 

 Phryganodea and the Semblodea, whose larvae inhabit water. Both 

 breathe during this state only through branchiae,, which in the former 

 consist of two leaves placed on each side of each abdominal segment, 

 but varying in form according to the genera, but in the latter they 

 appear as simple or plumose, tolerably long processes, which consist of 

 several joints, becoming gradually acuminate, upon the under surface 

 of which the tracheae ramify, protected by two rows of setae f. 



Branchiae seem very general in the family of the gnats, among the 

 Diptera, as they are found not only in the larvae but also in the pupae. 

 This is the case in the genus Chironomus, whose larvae described above 

 breathe through exterior tubes, but whose pupae are furnished with 

 two radiating fasciculi of branchiae at the thorax (PI. III. f. 6.). These 

 branchial fasciculi are seated close to the spot where later the first spiracle 

 of the thorax is found, namely, between the pro- and meso-thorax. 

 The same is the case in the genus Simulia ; the former has air tubes 

 at the anal end as well as at the thorax, the latter two large branchial 

 fasciculi between the pro- and meso-thorax (PI. III. f. 9 and 10 |). The 

 reversed relations obtain in the genus Anopheles, whose larva, described 

 as a remarkable water animal, first by Goeze , and afterwards by 

 Lichtenstein ||, but which G. Fischer IF ascertained to be the larva of this 

 gnat, bears hairy branchiae at its anal end, but whose pupa is provided 



* Suckow in Heusing., vol. ii. part i. p. 55, &c. PL I. and II. 



t Ib., p. 27. PI. III. f. 24. 



t Compare Thon's Archiv. der Entomologie, vol. ii. no. ii. PI. II. 



Beschaftigungen der Berliner Gesellsch. Naturfors. Freunde, vol. i. p. 359. PI. VIII. 



|| Wiledeniann's Archiv. fur Zoologie und Zootomie, vol. i. No. i. p. 108. PI. III. 



5f G. Fischer, Sur quclqucs Diptcres de Russie. PI. I. f. 1 16'. 









