Revision of the Notonectide. 407 
lobes always subequal in ordinary forms; generally unequal 
in the leucochroic varieties (ochrothoe, var. nov.), and rarely sub- 
equal (tearca, var. nov.). A/a nervures rich brown. Pedes : 
intermediate cox black, tibial spur small, rather blunt. Ab- 
dominis dorsum: segment 1 black, 2-5 violet-brown (the fifth 
apically black), 6 blackish, genital segments greenish-testaceous, 
all the segments more or less dull blackish laterally. Venter vary- 
ing from green to black, carina and cilia black. 
Long. 8-13 mm.,* lat. pron. 4-4°7 mm. 
Type. Uhler coll. 
Hab. America, ‘exclusively Western” (Uhler in 
litt.) ; California (Uhler’s and my coll.) ; Mexico (Paris 
and Stockholm Mus., Noualhier coll.) ; Colombia (Paris 
Mus.). Var. melena: Mexico (Noualhter coll.). 
This species cannot be mistaken for any other; the 
small, short head, the flat eyes with the anterior margins 
receding much as in typical N. insulata, the robust pro- 
notum and the structure of the notocenhalon at once 
distinguish it. 
Allusion has already been made to what I suppose to 
be concolorous varieties of this species. ‘There are, as 
indicated above, two forms; those with subequal mem- 
brane-lobes, diifering from the type only in the colour, 
which is (except the eyes, unguiculi, segment-junctions, 
&c.) entirely pale luteous. ‘his form | have seen only 
from Mexico (in the Stockholm Mus. and in the Paris 
Mus., where it was labelled ‘ americana,’ by Fallou). 
The other forms, also luteous, differ from the type in that 
they have unequal (both in width and length) membrane- 
lobes, and are much commoner (being noted from Mexico 
and Colombia). ‘They furthermore differ among them- 
selves in the shape of the pronotum. In nearly every 
case the lateral margins are almost perpendicular to the 
apical and basal margins and parallel to one another, 
while the humeral margins are not separable from the 
posterior margin. ‘here are, however, gradations to the 
usual shape. Prof. Uhler informs me that in the U.S. 
National Museum there is a specimen of this species 
pure ivory-white, and the above-mentioned luteous 
examples are probably this colour when fresh. 
* The smallest length given is that recorded by Uhler (/. ¢., 
p. 293), and 10°5 mm. is the smallest I have examined. 
