This rostrum is composed of three joints, and contains four 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 instruments, that the Nepa pierces and sucks little aquatic insects, not even sparing its own species. Its wound 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, elongated, 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 everywhere in stagnant waters in spring. It is brownish, carnivorous, and very voracious.
Fig. 76.—Corixa striata.
We must now mention the genus Corixa, of which one species, the Corixa striata, is 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 naturalist, M. Virlet d'Aoust, has published the following details on this subject:—
"Thousands of small amphibious flies," he says, "flit about in the air on the surface of lakes, and diving down into the water many feet, and even many fathoms, go to the bottom to lay their eggs, and only emerge from the water probably to die close by. We were fortunate enough to be present at a great fishing or harvest of the eggs, which, under the Mexican name of hautle (haoutle), serve for food to the Indians, who seem to be no less fond of them than the Chinese are of their swallows' nests, which they resemble somewhat in taste; only the hautle is far from commanding such high prices as the Chinese pay for their birds' nests, which for that reason are reserved entirely for the tables of the rich; while, for a few small coins, we were able to carry away with us about a bushel of the hautle, a portion of which, at our request, Mme. B—— was kind enough to prepare for us.
"They dress these in different ways, but generally make a sort of cake, which is served up with a sauce, to which the Mexicans give a zest, as they do indeed to all their dishes, by adding to it chilié, which is composed of green pimento crushed. This is how the natives proceed when they are fishing for hautle: they form with reeds bent together a sort of fasces, which they place vertically in the lake at some distance from the bank, and as these are bound together by one of the reeds, the ends of which are so arranged as to form an indicating buoy, it is easy to draw them out at will. Twelve to fifteen days suffice for each reed in these fasces to be entirely covered with eggs, which they thus fish up by millions. The former are then left to dry in the sun, on a cloth, for an hour or more; the grains are then easily detached. After this operation, they are replaced in the water for the next hautle harvest."