This section is from the book "General Outline Of The Organization Of The Animal Kingdom, And Manual Of Comparative Anatomy", by Thomas Rymer Jones. Also available from Amazon: A General Outline of the Animal Kingdom and Manual of Comparative Anatomy.
Rest, these are folded both in a transverse and longitudinal direction. The anterior wings are of a denser texture, resembling leather or parchment. To this order belongs the common House-cricket (Gryllus domes-ticus), of which, as well as of its eggs, larvae, and pupa, figures are here given (fig. 145).
This order comprises the Cockroaches, in which the wings are four in number when they exist; but they are generally of equal size, and never folded.
Fig. 145. Gryllus domestieus.
The larva is a worm either with or without legs. The pupa is quiescent; or if it moves, it does not eat.
Insects having four equally large or equally long wings with reticulated nervures, and mouths provided with strong lateral jaws. The most perfect examples of this order are the Dragon-flies (Libellula), the largest of the insect inhabitants of our own country. The perfect insect (fig. 146), equally remarkable for its beautiful form, powerful flight, and carnivorous habits, is among the most formidable tyrants of its class; while the larvae, which abound in our ditches and stagnant pools, are eminently destructive to their aquatic companions. The larva (fig. 147, b) possesses six articulated legs; while the pupa (a), which certainly forms an exception to the general rule given above, is not only furnished with rudimentary wings, but is eminently rapacious, and possesses in the structure of its mouth, to be described hereafter, peculiar facilities for gratifying its bloodthirsty disposition.
(762). In other orders, the wings are always unequal, - the posterior, and sometimes both pairs, not unfrequently being wanting.
Fig. 146. Dragon-fly.
a. Mouth adapted to sucking.
Instead of posterior wings, we find in this order pedunculated appendages called halteres or poisers. The mouth contains a soft proboscis, and is usually armed with several seta) and provided with a pair of palpi: of such the common House-fly affords a familiar instance.
The insects belonging to the Lepidopterous order are possessed of four wings, which are generally covered with microscopic scales, frequently exhibiting the most beautiful colours. The larva) are provided with feet and a distinct head; the mouth of the perfect insect is a long spiral proboscis.
(765). The Butterflies, so conspicuous for their beauty, are well-known representatives of this order; and the usual forms of these insects in the larva, pupa, and imago state are familiar to all (fig. 148, a, b, c.) ft. Mouths with distinct biting jaws.
With two wings.
Possessing four naked wings traversed by ramose nervures. Larvae generally without head or feet, but sometimes with both. Wasps, Bees, etc.
In this last order, the anterior wings are converted into dense horny cases or elytra, beneath which the posterior pair, adapted to flight, are folded up when the insect is at rest. The larvae possess a head, and are sometimes provided with feet, but not always.
(768). The Coleopterous division of the insect world embraces the extensive tribe of Beetles, both terricolous and aquatic; of the former we have an example in the common Cockchafer (Melolontha), of which a figure is here given, as well as of the different stages of its development (fig. 149, a, b, c, d, E)1.
(769). Having thus introduced the reader to the chief orders composing the vast class of Insects, our next object must be to examine more in detail the principles upon which these animals are constructed, both as regards their external organization and the nature and arrangement of their internal parts. We shall speak of them in the first place only in their perfect condition, leaving all observations relative to the metamorphoses to which they are subject for subsequent consideration.
Fig. 147. Metamorphoses of Dragon-fly.
1 It would be foreign to our present purpose to do more than enumerate other Orders of Insects which have been formed by different authors. Of these, the following are the most important: -