Wings four, generally covered with scales; the anterior pair slightly superior in size; mouth suctorial, the maxillæ forming a spiral tongue, which is coiled between the large labial palpi when not in use; other oral organs rudimentary. In many instances the whole mouth and alimentary canal are more or less obliterated, a considerable number of the species taking no food in their {7}final state. The larvæ always possess a distinct head and six thoracic legs, and in addition a variable number of prolegs are often present on the abdominal segments. Pupa inactive, the limbs of the future insect being usually indicated by lines in the integment. This Order contains all the varied tribes of Butterflies and Moths. (Plates VIII., IX., X., XI., XII., XIII.) ORDER V.--NEUROPTERA. Wings four, of equal size, membranous, and traversed with numerous branching ribs; the mouth masticatory, and in many instances but slightly developed. Larva with a distinct head and three strong thoracic legs; chiefly carnivorous. Pupa inactive; the limbs very perceptible and loosely applied to the body, but incapable of distinct motion. A small Order, comprising the Stoneflies, Lace-wings, Ant-lions, &c. (Plate XIV.) ORDER VI.--ORTHOPTERA. Wings four, of nearly equal size; the anterior pair often more or less leathery, but with distinct veins. The larva and pupa closely resembling the imago; the latter with rudimentary wings. In the instances where these organs are wanting in the mature insect, the metamorphosis merely consists of a series of moultings, and it is consequently a matter of some difficulty to determine when the insect is full-grown. This Order is of small extent; it includes the Earwigs, Cockroaches, Grasshoppers, Crickets, Termites, Dragonflies, Mayflies and Perlidæ; the last four being transferred from the Neuroptera of most authors. The minute species of Mallophaga and Thysanura will also come under this heading. (Plates XV., XVI., XVII., XVIII., XIX.) {8}ORDER VII.--HEMIPTERA. Wings four, in some cases wholly membranous, but in a large proportion of the families the basal portions of the anterior pair are horny, and form protective cases for the other pair when not in use; mouth suctorial, consisting of an elongate rostrum, enclosing four fine setæ. The larva and pupa resemble the imago, the latter being active, with rudimentary wings. In a few instances, a slight divergence from the parent form is shown in the preparatory states (Cicadas, &c.). This is a small Order, containing the Cicadas or "Singers," Bugs, Plant Lice, and all the suctorial animal lice. (Plate XX.) After the Orders, the divisions to be considered are the Groups, Families, Genera and Species. Groups are large divisions immediately subordinate to the orders, and consist of a number of _kindred_ families. They are of great assistance to the student in dealing with the very large Orders, such, for instance, as the Coleoptera.