Revision of the Notonectide. 405 
near the Pacific Coast, down which it spreads to Lower 
California and the highlands of Mexico.” It seems, 
further (from what Prof. Uhler writes) that while 
N. wndulata, Say (q.v.), is a Notonecta of the plains 
more especially, in warm ponds and streams, N. asu- 
lata is an insect rather of the hills, in cold pools. 
“The pond [i.e., where N. undulata was abundant] is 
exposed to the sun’s rays, and the water becomes 
mostly warm. At the western end, however, the pond 
is supplied with cold, spring water, and at that end 
lives the Notonecta insulata.” And again: “It seems to 
belong to the foot-hills and high plateaux of the Rocky 
Mountains west of the Mackenzie River; but it was not 
brought in from the plains.’ From the specimens I 
have examined, the very ruddy examples seem to occur 
principally in California, Colorado and Mexico, while the 
paler and rather larger forms come more frequently from 
the Eastern States. Fieber (/. ¢.) records N. rugosa from 
Brazil. 
Very like N. glauca, but at once distinguished by the 
stracture of the head. ‘There are (as in N. glauca) two 
somewhat dissimilar forms of eye in this species. Usually 
the notocephalon is short and the eyes are small, curving 
away from the vertex suddenly ; occasionally, however 
(and especially in var. geala), the eyes are more quadri- 
lateral and larger, and the notocephalon is longer. 
In Signoret’s collection there is a specimen labelled 
“ N. rugosa” by him, from Canada, which I cannot satis- 
factorily place in any species. It has the cephalic struc- 
ture of N. lutea, Miill., but is rather less robust pos- 
teriorly and has the ruddy dorsum always present in NV. 
insulata; the membrane lobes are unequal, as is usual in 
leucochroic individuals, and the hemielytra are greyish 
yellow-green. It seems best, till further evidence is 
obtainable, to regard it as an aberration from the present 
species. 
4. Notonecta lactitans, Kirk. 
Notonecta lactitans, Kirk., 1897, Ann. Mag. N. H. (6), 
xX., ps 08. 
Head: notocephalic lateral margins almost parallel, vertex 
about a fourth wider than synthlipsis; base of the eye about half 
as wide again as synthlipsis. Pronotal humeral margin well sepa- 
