HETEROPTERA. — HYDROCORISA. 457 
drometride, Acanthiide, Reduviide, Cimicide, Tingide, Capside, 
Lygzide, Coreidz, and Scutelleridz. 
The first section, Hyprocorisa, is entirely composed of aquatic 
species, in which the antenne are very short, and concealed in cavities 
beneath the eyes; their legs are more or less fitted for action in the 
water, being generally ciliated in the posterior pairs, with rarely 
more than 2-jointed tarsi, whilst the fore legs are short and fold, form- 
ing a pair of claws, whereby the insects seize their prey, which consists 
of other insects. The eyes are often of a very large size. There is 
considerable diversity in the structure and movements of the species 
of this section ; Notonecta and its allies being admirably formed for 
swimming, whilst the Nepide are very slow in their movements in the 
water, their legs scarcely serving them as oars; and yet they are 
equally predaceous with the rest. Living in an element not fitted 
for respiration, they are compelled to resort to its surface con- 
tinually to obtain fresh supplies of air; this is easily effected in the 
Nepide and Ranatre, by the assistance of the two appendages at the 
extremity of the body, which conduct the air to the two spiracles 
placed at the sides of the anus, which, from the researches of 
Dufour, are the only ones the insect possesses, the others, although 
placed in the ordinary situations, being merely rudiniental.* In the 
Notonectide, the extremity of the body is thrust out of the water, 
whereby a supply of air is introduced beneath the wings and the upper 
surface of the abdomen, where it is retained by the rows of hairs with 
which the segments are dorsally furnished, at least in Notonecta. 
(Dufour, Anat. Hémipt. pl.’7. f. 94.) The connection of these insects 
with the Aurocorise is admirably effected by the genera Galgulus, 
Pelogonus, and especially by means of my genus Aphelocheirus, as 
subsequently noticed. 
Nearly all the Hydrocorise are of a dull brown or obscure black 
colour. 
* See the observations of M. Spinola, referred to beneath, relative to the respir- 
ation of the Belostome. 
The insects of this section have afforded to M. Behn the discovery of the cir- 
culation ofa fluid through their legs. (See Ann. Soc. Ent. de France, 1835. p. 55. 
App.) This discovery has been denied by M. Dufour, whilst M. Wesmael has 
confirmed it, explaining Dufour’s denial of the fact by stating that he had ex- 
amined them in cold weather, in which M. Wesmael finds that the phenomenon is 
not visible. (Trans. Ent. Soc. vol. ii. p. 17.) 
