"§> 342. THE INSECTA. 435 



thin cutaneous membrane, and containing one or several finely-divided 

 trachean trunks. These trachean branchiae are either isolated, or fasci- 

 culated ; in this last case, they are often digitiform, or penniform, and their 

 ultimate ramifications are usually deficient in the spiral filament. All the 

 air-vessels which these branchiae contain, arise from the larger trachean 

 trunks. These branchiae occur with various Tipulidae, with a Nijmphula, 

 with the Phryganidae, Sialidae, Ephemeridae, Perlidae, Libellulidae, and 

 with the Gyrinidae. 



This trachean system is most simple with the larvae of Tipulidae of the 

 genera Chironomus, Taiiypus, Corethra and Simulia, as also with some 

 larvae of the Phryganidae, of the genera Rhyacophila and Hydropsycke, 

 where the tracheae, instead of forming cutaneous appendages, are sub- 

 cutaneous and can therefore extract air from the water. The larvae of Core- 

 thra are distinguished for having in the thorax and abdomen, directly 

 beneath the skin, two adjacent trachean vesicles, by means of which, very 

 probably, the necessary renewal of air takes place. '^' With the pupae of 

 Simulia, there are two branchial tufts on the sides of the prothorax, com- 

 posed, each, of six to eight long caecal tubes, which contain each a single 

 simple trachea deficient in the spiral thread.*-' Of the various larvae of the 

 Lepidoptera, living under the water, that of Nyinphula stratiotalis, alone, 

 has trachean branchiae. These consist of fasciculate filaments situated on 

 the sides of the abdominal segments.'^' With the larvae of Sialis, each of 

 the six, seven or eight abdominal segments has upon its sides an articulated, 

 filiform thread, containing a trachean vessel, and which may, therefore, be 

 regarded as a trachean branchia.'** Most of the larvae and pupae of the 

 Phryganidae, have, at the same points, one or two filiform, trachean 

 branchiae, rarely ramified, and united in groups of from two to five, which 

 stand out towards the back.'^' With those of the Ephemeridae, each of 

 the anterior abdominal segments has a pair of these branchiae which are 

 sometimes ramified in the most varied manner, and sometimes consist of 

 two kinds, some being laraelliform and alternating with the others which 

 are fasciculate.'*^* With all the Ephemeridae, these organs have move- 

 ments which are sometimes slow and rhythmical, and sometimes rapid and 

 oscillatory. 



With the Perlidae, the branchiae are filiform, ramified, and situated on 

 the three thoracic segments of the larvae and pupae, or bound together in 

 several short fasciculi which cover the base of the legs.''* 



Among the Libellulidae, the larvae and pupae of Agrion and Colo- 



1 See Reaumur, Mem. loe. cit. V. PI. VI. fig. 7, cliiae are ramose with Hydropsycke, and Rhya- 

 or Lyonet, Mem. du Mus. XIX. PL IX. fig. 14, cophila. 



15. 6 See Swammerdamm, Bib. der Nat. Taf. XIII.- 



2 See P^erdat and Fries, in Tlion's Entom. XV.; fteaM?/i!tr, Mem. VI. PI. .XLIL-XLVI.; De- 

 Arch. II. p. 66, 63, Taf. III. One must be careful, geer, Abhandl. II. Taf. XVI.-XVIII.; Suckow, 

 and not confound, as has sometimes occurred, the in Heusinger\s Zeitsch. II. Taf. III. fig. 21, 22 *, 

 hairy tufts of thes;; larvae for the tufts of tracheae. Carun, Eiitdeck. eiues Blutkreisl. loc. cit. Taf. III.j 



3 Sae Degeer, Abhandl. I. Abth. III. p. 85, and the figures of Pictet, Hist. d. Insect. Nivropt. 

 Taf. XXXVII. fig. 5, 6. Eph^-meriues. 



4 See Roesel, Insektenbelust. II. Insecta aquat. i" See the figures of Pictet, Hist. d. Nevropt., 

 Class. II. Taf. XXIII.; Deireer, Abhandl. II. Perlides. According to Newport (Ann. of Nat. 

 Taf. X.XIII.; Suckow, in Heusinger''it Zeitsch. Hist. XIII. p. 21, or Frorzf/j's neue Notiz. XXX. 

 n. Taf. III. fig. 23, 24 ; and Pictet, Ann. d. Sc. p. 179, or Ann. d. Sc. Nat. I. 1844, p. 183), 

 Nat. V. 1836, PI. III. During the passage into these branchial tufts persist, with Pteronarcya 

 the pupa state, which occurs with Sialis out of the rega/is, to the imago state. This would be a 

 water, these tracheae are cast off. very extraordinary anomaly, and should be coa- 



5 See the figures of PjcteJ, Ilecherch. pour servir firmed, for, from the observations of Neivport, it 

 & I'hist. et i. I'an.at. d. Phryganides, PI. II. &c.; does not appear that the tufts of hair situated on 

 and Degeer, Abhandl. II. Taf. XII. The bran- the thorax of this Perlide really preserve the struc- 

 ture of branchial tufts. 



