In the last chapter we dealt with Sheath-winged Insects--the Coleop´tera. Cockroaches belong to the Orthop´tera, or Insects with Straight Wings. The mouth-parts resemble those of Beetles. The chief differences that mark off the Cockroaches and their kin from the Beetles are the incomplete metamorphosis which the former undergo, and the character of the wings. Straight-winged Insects, when they leave the egg, differ little in shape from the adult, except in the fact that they have no wings; and these appendages are absent, or so small as to be useless for flight in many species. When wings are present the first pair are of little or no use for flight. They are not, however, hard chitinous sheaths, meeting in the middle line--that is, straight down the centre of the back--but of a flexible leathery or membranous substance, and they usually overlap each other at the tips. The hinder wings are large and nearly semicircular. The principal veins radiate from the centre to the circumference, like the sticks of a fan, and when the wings are folded up they lie straight along the upper surface of the abdomen. It is from this fact that the Order derives its name. There are two great groups, or sections, of Straight-winged Insects--those that run, like the Cockroaches, and those that leap, like the Grasshoppers. No Straight-winged Insect is aquatic. The Common Cockroach, now so abundant, is not a native, but an importation from Asia; though how it reached this country is not quite certain, probably by way of Holland. It seems to have established itself in London by the end of the sixteenth century, and some two hundred years later we find Gilbert White recording (in or before 1790) that ‘a neighbour complained that her house was overrun with a kind of black beetle, or, as she expressed herself, with a kind of black-bob, when they got up in the morning before daybreak. Soon after this account I observed an unusual insect in one of my dark chimney closets, and find since, that in the night they swarm also in my kitchen.... The male is winged, the female is not, but shows something like the rudiments of wings, as if in the pupa state.... They are altogether night insects, _lucifugae_, never coming forth till the rooms are dark and still, and escaping away nimbly at the approach of a candle.’ This description leaves no doubt as to what the ‘black-bobs’ really were. This name seems to have dropped out of use, and it would be well if ‘black beetle,’ in the sense of Cockroach, were also allowed to drop, for the term contains just as many errors as words.