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Class VI. HEMIPTERA; in which the perfect insect has four wings, a portion of the first pair often being leathery: the mouth is a tubular sucker, formed for extracting the sap of plants. Plant-bugs and plant-lice are the examples.

4. By passing through no uniform state,

ANISOMORPHA;

In which the Amorphous, Necromorphous, and Isomorphous characters appear, together with others not possessed by those groups. This group contains but one class of in

sects.

Class VII. NEUROPTERA; in which the perfect insect has four reticulated wings. Dragon-flies are examples, as are also the white ants at p. 57.

The first or Amorphous group, is again divisible into two minor groups, dependant on the circumstance of throwing off or retaining the prior skin when in the quiescent state; those which throw off this skin, as butterflies and moths, exhibit the eyes, antennæ, legs and wings of the future insect, and such a chrysalis is called pupa adermata: those which retain the prior skin, as flies, exhibit no trace of the situation of the limbs, and such a chrysalis is called pupa dermata.

The insects of the last section, possessing, as they certainly do, the extreme character of the Amorpha, nevertheless, as has previously been stated, testify a very evident approach to the neighbouring Necromorpha; for when the skin or covering of the quiescent insect is broken, a perfectly Necromorphous form is disclosed; and thus, though nothing could appear more different than the exterior appearance of the two, yet this examination proves that the

real difference exists only in the circumstance of one group retaining the covering of the previous state longer than the other group. If we select two well-known insects, the breeze-fly and the honey-bee, we shall find little or no difficulty in tracing the similarity. The grubs or maggots from which these insects proceed, are not very dissimilar; but the grub of the fly merely ceases to feed, becomes quiescent, and hardens externally (page 25, fig. d), while that of the bee ceases to eat, is walled in its cell by the workers, lines its cell with silk, casts its covering and becomes quiescent, every limb being distinct, detached, and perfect (p. 40), but enveloped in a delicately soft and smooth skin, and perfectly motionless. This is the true Necromorphous character. Now the breeze-fly, on the contrary, is Amorphous; but if a few days before the perfect insect appears, the hard and apparently inorganic case which covers it be gently opened, we find within a form precisely resembling the Necromorphous form of the bee just described; whence it appears clear that the so-called pupa of the bee and the fly are neither substantially nor numerically the same state. Every ecdysis or sloughing is a transformation; so that, calling the imago, as it certainly is, the ultimate state, then the so-called pupa of the bee is the penultimate, and the so-called pupa of the fly the antepenultimate. The difference is thus explained :-the fly, on assuming the perfect state, casts two skins, the bee only one.

In turning to the other section of the Amorpha, namely, the Amorpha adermata, including the butterflies, moths, &c., we find, on examining them in the quiescent state, abundant evidence that we have before us not only organized but animated beings; in these the grubs, before becoming quiescent, cast their covering in the same manner as the bee; but still, unlike that insect, retain two distinct coverings, thus resembling the Amorpha dermata. Both

these coverings are cast at the same time; the interior one, fine, semi-transparent, and delicately soft, must have been observed by all who have paid any attention to the rearing of Lepidoptera. Now the whole of the Necromorpha, as far as has yet been ascertained, finally undergo a single, and the whole of the Amorpha, on the other hand, a double ecdysis.

The Isomorpha, of which the common cricket is an example, have no quiescent state; nor can we find that they possess any state precisely equivalent to that portion of the lives of the two great groups we have been comparing. Their whole existence between the egg and the imago consists of a gradual series of approaches to perfection; and during this interval reproduction has been known to take place. No character is yet discovered by which the penultimate, antepenultimate, and prior states can be determined.

In the heterogeneous group, Anisomorpha, a group in metamorphosis, as in all other characters, equally related to the other three, we find a typical and distinct section in the dragon-flies. These, like the Isomorpha, have no quiescent state their preparatory state is aquatic, active and voracious: when arrived at the period for assuming the imago, they leave the water, and fixing their feet firmly to a slender stick or blade of grass, emerge from a double skin and fly away. The exterior skin is hard, corneous, and brittle; the interior soft, fine and pliable. The Mayfly, one of the Anisomorphous insects, has a metamorphosis still more striking, and one that has been deemed anomalous and unaccountable. In the antepenultimate skin it leaves the water, and attaches itself by the legs like the dragon-fly. Its antepenultimate skin then opens on the back; the insect emerges and flies away, leaving that one skin only that beautifully delicate skin which the dra

gon-fly quits simultaneously with the harder one, being still retained by the May-fly. Here then we have the strange fact of an insect's flying before it reaches the imago; that is, flying in its penultimate state. In twenty or thirty minutes at farthest it settles again, casts its skin, and becomes a perfect imago.

It thus appears that although, until the final ecdysis, no insect arrives at perfection, yet, before that period, even in the state immediately preceding, it may feed, run, and even fly; or may swim, crawl, barely move, or be without motion, without apparent life, or without apparent organization. It appears that the apparently lifeless or quiescent state may be entered without ecdysis; that ecdysis itself may be either single or double; that the states called pupa, in various tribes, are neither substantially nor numerically the same. That comparing the few insects herein noticed, the fly, the bee, the cricket, the dragon-fly and the May-fly, all of which represent great orders, we shall find it perfectly impossible to apply, if we aim at precision, any other than a numerical denomination to their intermediate states; and finally, therefore, that insects, like higher animals, have but three eras of existence, -the fœtal, the adolescent, and the adult.

As to the number of times ecdysis takes place in the life of an insect, little can be said at present owing to the carelessness and imperfection of our researches; and on this account it will be found safer to count downwards from the imago, than upwards from the egg. Although the contrary has been asserted, and perhaps generally believed, it yet remains to be proved, that the grubs of Diptera and aculeleate Hymenoptera undergo any ecdysis until full grown. The order Tenthredinites, on the contrary, and the Lepidoptera, change very frequently, with some exceptions; for

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example, the caterpillar figured below sheds its skin but once it produces the privet-moth.

These various facts, so simple, so obvious, so plain, so completely within the reach of the most cursory observer, proclaim that each variation in the number or manner of ecdysis is but another mode of metamorphosis; proclaim that metamorphosis, though in insects a complete and oftrepeated ecdysis, is but another instance of that constant loss and reparation of substance which is incident to all organized beings; proclaim the existence of a general uniformity of plan, with which the widest differences, the greatest discrepancies, are not only compatible, but are essential to perfect harmony, are the surest and safest guides to natural arrangement, and serve, like the keystone of an arch, to unite objects previously devoid of continuity; proclaim finally the greatness of Him whose will shapes the whole into perfection.

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