HEMIPTERA. 99 
pointed bristles. Two present on one side a sort of narrow sharp 
blade, and have teeth towards their base. Of the two others, the 
one is a thin smooth needle, the other is provided with hairs 
directed backwards and forwards. 
It is with this rostrum, which resembles a case of surgical in- 
struments, that the Nepa bites and sucks little aquatic insects, not 
even sparing its own species. Its bite is painful to man, but not 
in the least dangerous. With its four hind legs the Nepa swims, 
but at a very slow pace. It generally drags itself along the 
bottom of the water, on the mud, and does not avoid the hand 
put out to seize it. Its body is terminated by a tail, composed of 
two grooved threads, which, when applied together, form a tube, 
capable of being moved from side to side. Through this canal it 
breathes. the outer air; it puts the end of it out of the water, 
and the air enters it by inspiration. Some very small hairs, with 
which the interiors of the grooves are lined, interlace each other, 
and prevent the water from penetrating into the canal. It is 
probable that this same canal serves also for depositing the eggs. 
These last resemble small seeds, covered with points, and are 
buried in the stalks of aquatic plants. 
Next to the Nepa comes the Ranatra, with a cylindrical, elon- 
gated, linear body, with very long and very thin hind legs, and 
of which one species, which Geoffroy 
calls the ‘‘ aquatic scorpion with an 
elongated body,” is common every- 
where in stagnant waters in spring. 
It is brownish, carnivorous, and very 
voracious. 
We must now mention the genus 
Corixa, of which one species, the 
Corixa striata, 18 very common. 
This insect walks badly and slowly 
on land, but swims and cuts through the water with a prodigious 
rapidity. 
However, it is not to delay over this last species that we have 
here mentioned the name of this genus. Some insects which belong 
to it, and which are found in Mexico, deserve to be alluded to, 
on account of certain peculiarities which their eggs present. A 
H 2 

Fig 76.—Corixa striata. 
