The larva state immediately succeeds the egg, and is spent almost exclusively in feeding, the insect growing at a great rate, and being frequently compelled to change its skin. The pupa is usually completely quiescent, the insect being at this time quite incapable of any motion, except, perhaps, a slight twirling of its abdomen. Exceptions to this rule occur, however, in two of the orders, in which the pupa state does not differ materially from that preceding it. In the imago, or perfect state, the insect appears under its final form, with every organ completely developed. We will now consider the seven great divisions, or Orders, into which insects are divided, the complete knowledge of which is one of the most important elements in the entomologist's preliminary education. I trust that by a careful perusal of the following definitions, aided by references to the Plates, which illustrate numerous members of each order in their several states, the reader will be enabled to master the subject without much difficulty. ORDER I.--COLEOPTERA. Wings four; the anterior pair (termed elytra) horny and opaque, the posterior membranous, and employed in flight; mouth masticatory. The larva a grub with or without legs, but a distinct head always present. The pupa inactive, taking no food, the limbs of the future insect enclosed in distinct cases, and applied closely to the body. This is the largest of the Orders, and consists of all those insects popularly known as Beetles. (Plates I. and II.) {6}ORDER II.--HYMENOPTERA. Wings four, membranous, the posterior pair being the smaller, and connected with the anterior during flight by a row of minute hooklets; mouth masticatory, the maxillæ and labium being elongated, in many of the families, into a long sucking instrument or "tongue." Metamorphosis as in the Coleoptera. A large Order, containing the numerous tribes of Sawflies, Bees, Wasps, Ants, and Ichneumon-flies. (Plate III.) ORDER III.--DIPTERA. Wings two; the posterior pair represented by two minute clubbed appendages termed poisers; mouth a suctorial tube formed by an elongation of the labium, enclosing within it a variable number of setæ answering to the mandibles, &c., of biting insects. The larva without legs, a distinct head being often absent. The pupa inactive, the limbs of the imago firmly attached to the body, but plainly visible. Among the majority of species included in this Order the larval skin is not cast away, but envelopes the insect in a hard shell; the true pupa is consequently only visible on the removal of this covering, when it is found to closely resemble those in which no such arrangement occurs. The Order comprises the numerous Gnats and two-winged Flies. (Plates IV., V., VI., VII.) ORDER IV.--LEPIDOPTERA.