In order to save a considerable portion of the olive crop of these countries, M. Guérin-Méneville has advised hastening the harvest sufficiently for all the olives to be pressed at a time when the larvæ of the last generation, which would be preserved in the olives that are left, or in the earth, according to the climate, are still in the fruit. If a first operation were not sufficient to destroy them all, it should be repeated the following year. The sacrifice entailed by this practice would be amply compensated by a succession of good crops and the certainty of a sure and permanent profit. In fact, by an early gathering at least half a crop of oil is still obtained; whereas, by waiting for the usual period of gathering the olives, sufficient time is left for the larvæ of the Dacus to devour their parenchyma, which deprives them of the little oil that they might have yielded if their destruction had been accomplished earlier. This early gathering has the advantage of causing the destruction of a great number of larvæ, which will be so much towards diminishing the means of reproduction of the fly. III. HEMIPTERA. The Hemiptera are particularly distinguished from other kinds of insects by the form of their mouth, which consists of a beak, more or less long, composed of six parts: that is, of a lower lip, or sheath; four internal threads, representing the mandibles and jaws of the grinding insects, and which are the perforating parts of the beaks; and, lastly, of the upper lip or labrum. Owing to this apparatus, these insects are essentially sucking ones, and chiefly nourish themselves with the juices of vegetables, which they draw up with their beak. The wings of the Hemiptera are usually four in number; in some species they are membranous and similar to each other, and in others the upper are of rather harder consistency than the lower ones. In general, the former are quite different from the lower wings, and are only membranous at the tip, whereas the other part is thick, tough, and coriaceous. The Hemiptera are divided into two very distinct sections. The one is composed of insects whose beak grows from the forehead or upper part of the head, and whose anterior wings are half coriaceous and half membranous, having the base of a different texture from the extremity: these are the Heteroptera ([Greek: heteros], different; [Greek: pteron], wing). The other section is composed of those whose beak grows from the lower part of the head, and whose anterior wings are always of the same consistency throughout: these are the Homoptera ([Greek: homos], the same; [Greek: pteron], wing). We are about to give the history of these two sub-orders. HETEROPTERA. The insects formerly known by the general name of Bugs have been divided by Latreille into two large families, containing: the one the _Geocorisæ_,[19] or Land Bugs; the other the _Hydrocorisæ_,[20] or Water Bugs. [19] From [Greek: gê], the earth, and [Greek: koris], a bug.