ance which objects possess when covered with a slight coat of hear frost; it may be said to approximate to a blue grey.

Whites :-albous or albus is a pure white: whitish or albidus is a dirty or impure white: grey or canus, the colour of grey hair, and more properly confined to descriptions of hair cinereous or cinereus, the blue grey colour of ashes cretaceous or cretaceus, the white of chalk, or white with a slight tint of yellow ochre : niveous or niveus is a brilliant snowy white.

Besides these there are various metallic colours common in insects, as silvery or argenteus, brassy or aheneus, likewise written aneus, and then used to imply a bright gold green; the Latin word smaragdinus implies a still more intense degree of the same colour: coppery or cupreus, and steel blue or chalybeus.

The degree of intensity in a colour is usually implied by the addition of an adjective; thus saturatus implies that a colour is very deep and full; dilutus implies that it is pale again, lætus very bright, and obsoletus very dull or indistinct, are contrasted in the same manner, and may, by altering the termination, be used adverbially; thus lætè cupreus, obsoletè glaucus: saturatus and dilutus do not allow this change.

Of Distribution of Colour.-A diversity of colour occurs very frequently in the same insect, and the shape or limit of a colour is expressed by a descriptive word; as a spot or macula signifying a roundish or angular mark, not elongated in any direction: a stripe or plaga is the term used when the spot is more elongate: a fillet or vitta is a longitudinal stripe, and a band or fascia is a transverse one.

Shape. The terms used to express shape should be precisely in accordance with those employed by the Latin authors their copious language may readily be applied

to any figures with which we may meet, and technical nomenclature in this branch of the subject involves the description in obscurity instead of elucidating it.

Sculpture of Surface.-The characters impressed on the surface of the skeleton are highly important, and afford us excellent guides for the discrimination of species: a more minute detail of these appears indispensible: the following are the principal variations.

Smooth, lævis or lævigatus, is when the surface is perfectly smooth, without depressions or elevations: shining, nitidus or lucidus, when the surface is polished as a mirror: rough, asper or scaber, when covered with an irregular rugosity: pustulose or pustulosus, when covered with pustules resembling those occasioned by the small-pox: muricated or muricatus is when these pustules are pointed, and echinatus when they are produced into spines: verrucose or verrucosus, when covered with tubercles resembling warts: punctured or punctus is when the surface has the appearance of having been thickly punctured by the point of a pin, the pin not passing through, but simply making impressions: punctured in lines or striopunctus is when these punctures are arranged in longitudinal lines: reticulate or reticulatus, when tolerably smooth, yet covered with something like net-work: vermiculate or vermiculatus, when covered with tortuous markings, like worm-eaten wood: striate or striatus is when marked with longitudinally impressed lines, and punctostriatus is when these lines are themselves punctured: canaliculate or canaliculatus is when the impressed lines are coarser and deeper than the foregoing, and sulcate or sulcatus is when they are still deeper, resembling furrows: lineate or lineatus has lines in the same degree as striatus, but the lines, instead of being impressed, are raised above the surface: keeled or carinatus is when these raised lines

are fewer and more elevated: and chained or catenatus is when the space between two impressed lines is divided into oblong elevations, and is supposed to resemble a chain.

Clothing of Surface.-A surface is called tomentose or lanuginosus when covered with a thick down: sericeous or sericatus when the down is short, thick and silky: villose or villosus when the surface is covered with longer and more distinct hairs: hirsute or hirsutus when covered with long shaggy hair: crinite or crinitus when the hair is very long and thin: squamous or squameus when covered with distinct scales.

In the Pteracantha fasciata, the insect figured below, the antennæ may be termed slightly serrated; the elytra are slightly carinated, and are distinguished by an acute spine at their lower extremity or apex: the light band across the elytra is called a fascia,-hence the term fasciata.

Larva of Ephemera marginata, magnified. The central shaded line represents the great dorsal channel of the blood. The lateral branched lines the trachea.

CHAPTER III.

ON THE INTERNAL ANATOMY OF INSECTS.

OF THE Muscles of Insects.-Muscle is a substance which yields to the touch: it consists of two parts; the body of the muscle, which is fleshy; and the extremities and coating of the muscle, which are tough, strong, and elastic, and are designated as tendon. The surface of muscle is a beautiful microscopic object: it presents a series of exceedingly fine transverse lines, which, in contraction, assume an undulated form. The fibre of muscle is much

the same in every animal, from man to the most minute animalcule. The attachment of muscle is solely to the osseous plates or bones, which constitute the external covering of an insect; in these they originate precisely in the same manner as the muscles in the human frame are attached to, and originate in, the bones.

The bulk and form of muscles in insects are beautifully apportioned to the offices they are required to perform; and unusual bulk in any part of an insect generally implies the presence of unusually developed muscle, and the object for which it is developed may frequently be ascertained. We have before seen, that the fore wings arise from the mesothorax, and the hind wings from the metathorax: these segments vary greatly in size, and this variation depends so precisely on the powers of flight possessed by each pair of wings, that an insect anatomist, on regarding these two segments alone, would at once decide on the relative power of the wing which they had borne. In flies, the fore wings alone are used in flight; the hind wings are rudimental; the whole bulk of muscle, therefore, required for flight, is placed in the mesothorax: in beetles the hind wings alone are used in flight, and the bulk of muscle is consequently transferred to the metathorax. It happens in some moths, that one sex flies and the other does not; and in these the different size of the wing-bearing segments proves the provision of muscle to be for the purpose of flight. In the common ant, the little worker never leaves the ground; wings, therefore, would be an incumbrance to it. We find that its pro- meso- and metathorax are very small and insignificant segments, while the mesothorax of the productive female is the largest segment in her body, because it is one of her duties to perform a long flight, and to use the wings which that segment bears. The muscles in those wing-bearing segments which