LOCAL DISTRIBUTION OF INSECTS. 501 
fect. Amongst the Eupodina*,—Elaphrus, Notiophilus, 
and Bembidium frequent humid places, as the banks of 
rivers and ponds; and in such a station, under the roots 
of Potentilla anserina, Polygonum, &c. if you should 
be fortunate enough to find Omophron limbatum, which 
connects the Eupodina with the Eunechina, you will 
make a valuable addition to the list of British insects. 
In the waters also: you will meet with many Hetero- 
pterous Hemiptera ; as Gerris, Hydrometra, and Velia 
Latr., and all the Hydrocorise or water-bugs. On aqua- 
tic plants the larvee of some Lepidoptera feed, as Bo- 
tys stratiotata, potamogata, &c. Those also of the Tri- 
choptera 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 gra- 
tify your curiosity. Though few or no Hymenoptera fre- 
quent this element, vast numbers of Diptera are there 
alone to be met with in their preparatory state, particu- 
larly the gnats. We learn from Humboldt a curious fact 
with respect to those of South America, or the ancudos ; 
that, with some exceptions, these pests do not frequent 
those rivers called by the natives black waters, but only 
those which they name whzte waters». Of the Aptera, the 
genera Hydrachna, Elais, and Limnochares are purely 
aquatic. Several spiders will walk over the water; and 
one species (Argyroneta aquatica) inhabits it. The stag- 
_ nant waters in your vicinity will produce different species 
from running ones. ‘Thus Haliplus elevatus, &c. inha- 
bits only the Jatter, while the majority of the Dytiscide 
* See above, p. 392. » Personal Narrat. HE. T. v. 91—. 
© See Vou. I. p. 473—. 
