LOCAL DISTRIBUTION OF INSECTS. 513 
water. Lixus paraplecticus, Tanysphyrus Lemnce, Ba- 
gons atrirostris, are of this description. A species of 
Ceutorhynchus of Germar's third family (C. Natator K.) 
swims well. On aquatic plants you must look for Hclo- 
des and the splendid Donacice, which, living on sub- 
merged shoots and roots of these plants in their larva 
state, continue to attend them when perfect. Amono-st 
the Eutreckma*,—Elapkrus 9 Notiophilus, and Bembi- 
dium frequent humid places, as the banks of rivers and 
ponds; and in such a station, under the roots of Pote?i- 
tilla anserina, Polygonum, &c. if you should be fortunate 
enough to find Omophron limbatwn, which connects the 
Eutrechma with the Eunech'ma, you will make a valuable 
addition to the list of British insects. In the waters 
also you will meet with many Heteropterous Hemiptcra; 
as Gerris, Hydrometra, and Velia, and all the Hydrocorisce 
or water-bugs. On aquatic plants the larvae of some Le- 
pidoptera feed, as Hydrocampa stratiotata, potamogata, 
&c. Those also of the Trichoptera must be sought for 
in the water : and if you should feel inclined to see an 
interesting collection of their very curious cases, Mr. 
Sheppard of Wrabness can gratify your curiosity. 
Though few or no Hymenoptera frequent this element, 
vast numbers of Diptera are there alone to be met with 
in their preparatory state, particularly the gnats. We 
learn from Humboldt a curious fact with respect to those 
of South America, or the Zancudos ; that, with some ex- 
ceptions, these pests do not frequent those rivers called 
by the natives black waters, but only those which they 
name white waters b . » Of the Aptera, the genera Hy- 
:i See above, p. 401. b Personal Narrat. E.T. v. .91—. 
vol. iv. 2 L 
