168 ANATOMY. 



Several, or at least two leaves, are found at each place, so that each 

 segment of the body has never less than four branchial leaves. They are 

 generally uniform, but an instance is known (Ephemera Jusco-grisea, 

 De Geer*,) in which one of the branchiae is lamellate and the other 

 is a fasciculus of filiform ones. 



If we look to the orders in which branchiae are found, we shall 

 speedily see that they are not rare, and, indeed, that the majority of 

 larvae which live in water breathe by means of gills. 



The following are the genera whose larvae thus respire : 



Among the Culeoptera we find hairy branchiae in the larvae of the 

 whirlwigs (Gyrinus t), which rise from the sides of each segment, and 

 clothe the body as simple, tolerably stiff, hairy processes. The closely 

 allied Dyticus have no gills, but spiracles, which lie contiguous to the 

 anus ; the larva of Hydrophilus piceus likewise breathes through 

 spiracles thus placed, but the larva of Hydrophilus Caraboides, has, 

 according to Roesel's figure +, ramose branchial fasciculi on each abdo- 

 minal segment. 



The Orthoptera never live in water either as larvae or as perfect 

 insects, they have consequently only spiracles as the exterior organs of 

 respiration. 



Many of the Hemiptera, both in their larva and perfect state, live in 

 water, but branchiae have never yet been observed in them. Both young 

 and old, when they wish to breathe, come to the surface of the water, 

 and receive air through the spiracles. Nepa and Ranatra have air 

 tubes, which we have mentioned above. 



Whereas in the orders of the Dictyotoptera and Neuroptera the 

 branchial apparatus is very general. In the first of these orders, the 

 larvae of the Ephemera and Libellulce live constantly in the water, and 

 have branchiae. In the larvae of the Ephemerae, they lie at the sides of 

 the body, four upon each segment, and they consist of small leaves of 

 various forms. In Ep.fusco-grisea one branchia is a leaf, and the other 

 a fasciculus ; in Ep. vulgata both are leaves, very narrow, and clothed 

 at the margin with long fine hairs. The branchiae of the larvae of the 

 LibellulcB are not placed at the sides of the abdominal segments, but 

 upon or within the last segment ; and in Agrion they form three large 





 * De Geer, M^moires sur les Insectes, vol. ii. part ii. p. '29. PL XVIII. t'. '.'>. 



f Ib , vol. iv. PI. XIII. f. 1C 19. 



J Inscctenbelustignngen, vol. ii. Vv';is>cr-In<crtrn d. Ki>t. Klassc, p. 3'2. Fl. IV. 



DC Gccr, ih. PL XVI. f. ;5. 



