Billeder på siden
PDF
ePub

ORDERS OF INSECTS.

225

LESSON 100.

Orders of Insects.
Per'forator, a part of some insects with which they bore various

substances in order to admit their eggs. Farina'ceous, mealy, resembling the farina of flowers. LINNÆus divided insects into seven orders. His divisions are founded upon the presence or absence of wings, their number, their texture, their arrangement, and the nature of their surface. The first order (colcop'tera) has four wings. The upper pair consist of a hard, crustaceous or horny substance, and cover or defend the under pair, which are of a more soft and flexible texture, and are folded beneath them. This is the most numerous and best known kind of insects; and many of them are very remarkable for the singularity of their forms and the beauty of their colours. The various insects known under the name of beetles and winged bugs are included in this order,

The second order (hemiptera) has likewise four wings; but the upper pair is not of so hard a texture as those of the beetle tribe. They are more like fine vellum, and, at their extremities, terminate with a membranous edge, which resembles the substance of the under pair. They cover the body horizontally, and do not meet in a straight line or ridge, as they do in the first order. Among them are found the grasshopper and the locust.

The third order (lepidoptera) has four wings and comprehends the various kinds of moths and butterflies. Their wings are covered with a farinaceous powder, or rather with scales or feathers, disposed in regular rows, nearly in the same manner as tiles are laid upon the roofs of houses. The elegance, the beauty, the variety of colours, exhibited in their wings, are produced by the disposition and tincture of these minute feathers. When the feathers are rubbed off, the wings appear to be nothing more than a naked and often a transparent membrane.

The fourth order (neurop'tera) has four naked membranous wings, which are so interspersed with delicate veins, that they have the appearance of a beautiful net work. They have no sting. Of this order are the various species of

226

ORDERS OF INSECTS.

dragon fly, large and well known insects that frequent lakes and pools of stagnant water ; the Ephem'eral fies, which pass two or three years in the states of larva and chrysalis, but whose existence as winged and perfect insects is limited to a single day; and the Ant-lion and Ter'mites, the former celebrated as the destroyer of the common ant, and the latter for the ravages they make in some tropical countries.

The fifth order (hymenoptera) has four naked membranous wings, but destitute of that delicate, netted structure, which belongs to the last order. The females have either a perforator or a sting. In the domestic economy and mode of propagation of some of the species, there are circumstances which excite our admiration and astonishment. The ant, wasp, and bee belong to this order. They live in societies, greater or less in extent and number; and prepare habitations and nourishment for themselves and Offspring, with a forethought and provident care, excelled only by man himselt. In some of the tribes of this order, there is, beside the males and females, a third: sort called neuters, as among the ants and bees.

T'he sixth order (dip'tera) has only two wings, but beneath them are two cylindrical projections, which seem as if they were the rudiments of another pair. These have been called balancers or poisers, from being supposed to aid them in preserving an equilibrium during their flight. Between them and the wings themselves are found small membranous scales, one upon each side, against which the balancer strikes with great rapidity, whilst the insect is in motion, and causes that buzzing which is then observed. To this order belong some of the most troublesome and annoying of the whole animal creation, such as the various species of gnat, and the common fly. They are found in almost every part of the globe.

The seventh and last order of insects (ap'tera) includes a great variety that are destitute of wings. It is true that in the preceding orders are arranged many sorts of insects that are destitute of wings, but they are so arranged because in their general structure and habits of life they resemble the other members of the order. The Aptera, however, have no such resemblance, and are therefore placed by themselves. Some animals of this order cover the surface of

ORDERS OF INSECTS,

227

[ocr errors][merged small][merged small]

plants so completely as to produce the appearance of a discoloured change of structure.

The family of spiders (ara'nea) is not always arranged among insects, and strictly speaking their structure is different in some important particulars. They are distinguished from all other insects by the absence of the antennæ. They have generally eight legs, and are furnished with six or eight eyes, which enable them to see objects in several different directions at once. They are nourished generally by living prey, which they secure by means of a web, spun with much ingenuity. The threads, of which the web is composed, are produced from six little fleshy bunches, or muscular instruments, each of which contains about a thousand tubes, or outlets of threads, so extremely minute that many hundreds of them must be united before they form one of those visible ropes, of which the spider's web is composed. By means of their webs, many species of spiders, particularly when young, are able to transport themselves to a considerable distance through the air. In order to effect this, they ascend some eminence, and throw out a nuinber of webs.

These are raised up and carried along by the wind, and the animal being buoyed up by them is conveyed sometimes to a great height. In order to alight, they have only to disengage themselves from a part of their web, and suffer themselves to descend gradually to the ground. It is probable that they have recourse to this expedient, in part at least, for the purpose of catching insects for food. In autumn, the air is often full of the cobwebs which have been made use of for this singular mode of conveyance.

This fine filmy substance is called Gossamer ; and it is seen not only in the air, but is more observable in stubble fields, and. upon furze and other low bushes. Those who have ascended eminences for the purpose of observing the phenomenon, have frequently seen spiders floating by in the air, supported in the manner which has been described.

To the In.:ect of the Gossamer :-By C. SMITH.
Small, vieu less aëronaut, that by the line

Of Gossamer suspended, in mid air

Float'st on a sunbeam. Living atom, where
Ends thy breeze-guided voyage ? With what design
In ether dost thou launch thy form minute,

228

CRUSTACEOUS ANIMALS.

Mocking the eye? Alas! before the veil
Of denser clouds shall hide thee, the pursuit

Of the keen swift may end thy fairy sail.
Thus on the golden thread that fancy weaves

Buoyant, as Hope's illusive flattery breathes,
The young and visionary poet leaves

Life's dull realities, while seven-fold wreathes
Of rainbow light around his head revolve.

Ah! soon at Sorrow's touch the radiant dreams dissolve. Questions.-1. Upon what is the division of insects into orders ounded? 2. What are the characteristics of the first order ? 3. Second? 4. Third ? 5. Fourth? 6. Fifth ? 7. Sixth ? 8. Seventh ? 9. Describe the wings of butterflies. 10. Describe ephemeral flies? 11. What is worthy of notice in ants, wasps, and bees? 12. How is the buzzing of flies produced ?" 13. How do aptera insects often appear on plants ? 14. How are spiders distinguished from all other insects ? 15. How is the web of ihe spider produced ? 16. Describe the aerial excursions of spiders. 17. What is the gossamer, and where seen?

LESSON 101.

Crustaceous and Molluscous Animals. Mu'cous, slimy, viscous or glutinous. The Crustaceous animals have been sometimes included in the class of insects, to which they have indeed many strong points of resemblance. They deserve, however, a separate consideration, both on account of their size and importance, and of some anatomical differences of structure. They have articulated limbs, antennæ, and jaws, similarly formed to those of insects. But they breathe by means of gills, and have a regular, double circulation; in which particulars they differ from insects. Among the most familiar examples of this class are the lobster, craw-fish, and what is usually called the horse-shoe. They are covered by a pretty thick, firm shell, which envelopes them completely. As this shell is incapable of growth, it is occasionally change ed, to make room for the constant increase in size of the animal. It is thrown off, and their bodies remain for a time entirely naked, and exposed in a soft and defenceless state.

MOLLUSCOUS ANIMALS.

229

In this case, the animal generally retires to some place of concealment and security, and remains till the shell is restored by the deposition of calcareous matter on the external membrane of the skin, which becomes hard and firm, and finally takes the place of the old shell.

The Molluscous animals form a large and extensive class, but their structure, residence, and habits, are obscurely and imperfectly known. Among them are the cuttle-fish, oyster, clam, snail, and, in short, nearly all the testaceous animals, or shell-fish, as they are usually called, although they have no resemblance to fishes, and do not all inhabit the water. They are destitute of bones and articulated limbs. Their bodies are generally of a soft texture, and frequently, at first sight, appear to be little else than a simple mucous mass, without parts and almost without organization. In most instances they are completely enveloped in a fold or reflection of the skin, which is called their mantle. Sometimes there is only this simple membranous covering ; but more frequently there is a hard external shell, which serves as a retreat into which the animal may withdraw itself, and which it can carry about in all its changes of place. These shells differ exceedingly in shape, colour, and texture, in different species, and among them are found some whose form, polish, and splendid tints place them among the most beautiful objects in nature.

QUESTIONS.—1. In what points do crustaceous animals resemble insects? 2. In what do they differ? 3. What are examples of this class ? 4. What is said of the growth and casting of their shell? 5. What are examples of molluscous animals ? 6. What description of them is given?' 7. What is said of their shells? (Note. The study of those animals in the class mollusca which are characterized by a shell or calcareous covering has obtained the distinct scientific name of Conchology. The objects of conchology are separated into three divisions, namely, multivalves, or shells with many valves; bidaltes, or shells with two valves; univalves, or shells with one valve.]

20

« ForrigeFortsæt »