HEMIPTERA. - This order consists of insects of very varying structure. Primarily there are two great divisions, known as Heteroptent and Ilomoptera, by some considered distinct orders. The points in which they agree consist especially in an imperfect metamorphosis, and the structure rudiments of maxillary palpi. The tarsi have from one to three joints.

In the Heteroptera (or true Bugs) the anterior wings are horizontal, and composed of two distinct parts, the basal portion (or corium) being coriaceons, and the apical portion (or membrane, often undeveloped) being membranous with distinct longitudinal neuration, which latter is only faintly indicated in the coriaceous portion. In repose the membranous portion of one wing overlaps that on the other. The posterior wings are concealed under the anterior, folded, membranous, and with only few nervures. Apterous forms are not uncommon, and sometimes the posterior wings are wanting. This division is again divided into two, Gymnoccrata and O•yptoccrata, in the former of which the antenna are composed of few elongate slender joints, while in the latter the joints are still fewer, short and thick, and ordinarily concealed under the head. Modern writers have erected a multitude of small subdivisions which cannot be enumerated here. The Gymnoccrata are broadly divided into the following families, viz., Scutelleridx, Pentatomidm, Coreidm, Berytidw, Lygmidm, Capsidte, Dingididre, Redus-iticlza, Emcsidee, and Sear/idle, founded on different points in the structure of the antennas, rostrums sentellum of mesothorax, tarsi, Sze. They are terrestrial, and suck the juices of plants or animals. The entire family Reduradte are probably blood-suckers, and members of other families as above given are notorious for a similar habit, amongst which may be particularly noticed the germs Acastaia (including the Bed Bug); but the greater part are plant bugs. Most of them are remarkable for emitting a peculiar and often disgusting odour. The C3•yptoecrata are entirely water bugs, often of extraordinary form, and sometimes gigantic in size. They include the families Hydrometridte, Gerridte, Ncpidte, and Notoneetitte. They prey npon animals. One genus (Halobates) is remarkable for its pelagic -habits, being found on the surface of the ocean very far from land. Many others, such as Notonecta (Water Boatmen or Toe-Biters), Nepa, llanatra, &c., arc very familiar insects.

The Homoptera have the wings for the most part dellexed, and the anterior pair not separated into two parts. Often all the wings are membranous, with strong nervures ; in others the anterior pair is coriaceous. The division regarded as a whole is very polymorphic. The true Homoptera have three-jointed tarsi. They may be divided into Cieadidm (remarkable for the sound-producing organs at the base of the abdomen of the male), Fulgoridw (known as Lantern-Flies, but now known to produce no light ; having the head greatly prolonged in front), Lystridte, Oixiidee (comprising many little plant-hoppers), issidx, Derbidx, Flatidre, Tctliyonictrithe, Membracielte (often of most extraordinary forms), armpit's; (included in which is the Cuckoo-Spit Insect), Ledridee, and Jassidie, - all vegetable feeders. The more aberrant Homoptera include well-marked groups. The Psyllidm are small plant-sucking sanatoria insects with four membranous wings which lie longitudinally deflexed in repose, and with very narrow prothorax, and eight- to ten-jointed antenine ; they often occasion much damage ; the larvre are frequently covered with a cottony secretion. The ilphidte are the familiar Plant-Lice, the winged forms of which have those organs membranous, and often extended in repose. The antennae arc five- to seven-jointed. The diversity in form and habits is enormous, and, as is well-known, there are winged and apterous forms in the same species, and parthenogenetic generation of the most extraordinary nature ; and the same species may be both oviparous and viviparous.

Most of them void a sweet secretion from abdominal taws, known as honey-dew, for which they are " milked " by ants. The destruction they occasion to plants is very great ; as a now too familiar instance of this, the Phylloxera rustatrix of the grape-vine may be cited. Coe,cidee (or Scale Inseets) have the male two-winged, the female apterous, and living all her life as a fixed "scale" on plants, the organs being of the most rudimentary nature ; the eggs lying under the scale in great numbers ; the tarsi with only one joint ; parthenogenesis occurs also in this group ; the male in its earlier stages lives under a special scale. The Cochineal Insect is one of the best known in this group. The little family A/curette/re consists of minute insects covered with a white waxy secretion. They have four almost nerveless wings in both sexes, two-jointed tarsi, the abdomen without secreting tubes, and do not live under scales.

In the Hemiptera it is now the fashion to include the Anoplura, or true Lice (some also place here the Ma/fop/my/ or bird-Lice), a degraded form of this order, without metamorphosis. Ilere it is preferred to let them rest in this article, even although sonic writers do not consider them true insects. The month parts certainly have indications of a rostrum, and there are no palpi, and, but for the absence of metamorphosis, there would be little difficulty in fixing the positiou here as without doubt. All, as is well-known, are epizom parasites on man and other Mamnedia, each species being confined to a special host, while attempts have been made to prove that the I I ead- Louse (Parliculas eapitts) varies according to the races of men to which it is attached. Perhaps the Crab-Louse (Phth fries pubis) is regarded with greater disgust than is bestowed upon any other living creature.