GILL'S

TECHNOLOGICAL & MICROSCOPIC

REPOSITORY.

XXVIII.-On the Microscope. By THOMAS CARPENTER, Esq. With Remarks and Additions. By the EDITOR.

WITH FIGURES.

(Continued from page 78.)

London, February 8, 1830.

DEAR SIR, THE beginning of last June I'met with a cluster of eggs, attached to the leaf of a water-plant; they were disposed with so much symmetry, that I took them home to examine under my microscope, and found I had procured a very interesting object. I believed that they had been placed on the plant by one of the water-beetles; and wishing to ascertain the species, I placed that portion of the leaf to which they were agglutinated, on a small piece of cork, and which I floated on the surface of some water, placed within a tea-cup. In a few days the larvæ had left the eggs, and had crawled down the sides of the cork into the water: there were hundreds of them, and so exceedingly minute, that I could make out nothing without placing them under the object-glass of my microscope. I then found them to be the larvæ of a species of dyticus, and more interesting microscopic objects I have scarce ever met with. They were furnished with forceps or jaws at their heads similar to the dyticus marginalis. The minuteness of these larvæ rendered them fine microscopic objects, as they would bear a very high magnifying power, under which their internal structure was plainly seen.

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I have also met with clusters of similar eggs attached to the blades of grass, growing on the banks of the New River; and, by using the above method, have succeeded in producing larvæ from them, with precisely the same characters as those from the eggs found on the water-plants in ponds. I herewith send for your inspection the empty shells from which the above insects had come out; and also some perfect eggs, which I had dried, by heating them, in order to prevent the larvæ from coming forth. The characters on the external parts of these eggs you will find very curious; indeed, the eggs of all the insect tribes are highly interesting objects; the various shapes and markings upon them, are almost as diversified as the insects themselves. They are to be met with of various colours, some are found of almost every shade of yellow, green, and brown; a few are red, and others black. Green and greenish coloured eggs are not unusual; and they are sometimes speckled over with darker colours, like those of birds. Some are smooth, and others beset, in a pleasing manner, with raised spots. We are accustomed to see the eggs of different species of oviparous animals so nearly resembling each other in form, that the very term egg-shaped has been appropriated to this particular figure. Among those of birds, with which we are most familiar, the sole variations are merely shades of difference between a globular and an oval or ovate figure. The shapes of the eggs of insects, however, are confined to no such limited model. They differ often as much, both as to their shape, markings, and appendages, as one seed does from another. Their usual forms indeed are globular, oval, or oblong, with various intermediate modifications. We meet with them shaped like the common hen's egg; flat, and orbicular; elliptical, conical, cylindrical, hemispherical, lenticular, pyramidal, square, turban-shaped, pear-shaped, melon-shaped, boat-shaped, of the shape of a drum, &e. ; and sometimes of shapes so strange and peculiar, that we can scarcely allow their claim to the name of eggs! In

Kirby and Spence's excellent work on Entomology, plate XX., you will meet with a great variety, both in their shapes and markings, of the eggs of insects, of the accuracy of which there is no question; and, indeed, you may satisfy yourself thereon, by seeking for varieties of insect's eggs during their proper season. In the mean time, I send a few specimens from my collection, for your examination. Some of these are from the vapourer moth, and are curiously embedded in hair. The female moth is destitute of wings, and therefore cannot fly. The males are very shy, and difficult to capture. The method of taking them is very singular: a collector, having a female moth confined within a pill-box in his pocket, has only to go into the woods, and the males, by some powerful instinctive faculty, will find them out in that secluded situation, and, hovering over the collector, they are easily taken in his net. Mr. Stone, a celebrated entomologist, assured me that he has had females confined within a breeding cage in his yard in London, and the males have even found their way from the woods, over the houses, and alighted on the cage in which the females were confined! I have before remarked, that Mr. Samouelle stated that the males have even been known to enter the pocket of an entomologist, who had a female moth thus secured in a box! In many species of lepidoptera, the females are also destitute of wings, and the males are captured in a similar manner to the above.

With the eggs, I also send you a caterpillar; you will observe how curiously it is covered all over with hairs and feathers. Likewise specimens of the male and female moths. I also send a few eggs from the oak-egger moth; I have, from good authority, been informed of a singular circumstance in the economy of nature respecting the preservation of this species of insect. It appears, that the female lays a certain number of eggs at one time; the caterpillars are also excluded from them nearly all at one time; and after feeding their usual period, they pass into the crysalis state. The first year, a few moths only come forth;

the following year produces a few more; and again, in the next year, others come out; but it is not until the seventh year, that the whole are produced! Although it appears above that the caterpillars went into the crysalis state at about the same time. Does not this mode of preserving the species of insects show the mysterious ways of the Almighty even in his smaller works?

With these you will also receive a few eggs from the cabbage butterfly, the Atlas moth, and the magpie moth; the characters in these are very singular. Also some from the gypsy moth, very curiously embedded amongst hairs, produced from its own body, it thus forming a nest to lay them in; a wise provision of nature for the preservation of its offspring. Also some other eggs from the buff-tip moth; in the centre of each egg, you may observe an indentation or opening, which is covered over with a thin film or skin, to protect the caterpillar while within it, and also to afford it an easy way of breaking its way through the egg. There are likewise some other very singularly marked eggs, which I found attached to the twigs of the hazel and blackberry ; and some others which had been deposited upon a ripe

currant.

In order to point out to you the amazing number of caterpillars which are produced from a single moth or butterfly, and which, if not kept within due limits, would destroy all our vegetation, I send you the bodies of a moth and of a butterfly, laid open, and in which you will observe that every part of the interior is full of eggs. These are not solitary instances, as the bodies of all the female moths and butterflies are filled with eggs in the like manner.

In Kirby and Spence there is a very interesting statement of the number of eggs laid by various insects; the musca meridiana, a common fly, lays two; other flies, six or eight; the flea, twelve; the burying beetle, nicrophorus vespillo, thirty; may flies, under a hundred; the silk-worm moth, about five hundred; the great goat moth, cossas ligniperda, one thousand; acurus Americanus, more than a thousand;

the tyger moth, callimorpha caja, sixteen hundred; some cocci, two thousand; others, four thousand; the female wasp, at least thirty thousand; the queen bee varies considerably in the number of eggs that she produces in one season, in some cases it may amount to forty or fifty thousand or more; a small hemipterous insect, resembling a little moth, alcyrodes proletella, two hundred thousand. But all these are left far behind by one of the white ants, termes fatali, F. bellicosus of Smeathman, the female of this insect extruding from her enormous matrix not less than sixty eggs in a minute, which makes 3,600 in an hour, 86,400 in a day, 2,419,200 in a lunar month, and the enormous number of 211,449,600 in a year! Probably, indeed, she does not always continue laying at this rate; but if the sum be set as low as possible, it will yet exceed that produced by any other known animal in the creation. The sturgeon is said to lay 1,500,000 eggs; and the cod fish 9,000,000. In the British Museum there are several specimens of the above insect, whose abdomens are distended to an amazing size, they are completely filled with eggs.

I also send you the egg from a large species of grasshopper, and the bodies of two of these insects, which you will find are filled with eggs; together with a few eggs from the common gnat. With these you will likewise receive the head and thorax of a moth, which are covered with a profusion of delicate scales and feathers; together with parts of other moths, displayed as proper objects for the microscope. Likewise several minute moths, of most exquisite beauty, and which are profusely adorned with fine metallic coverings. Among these are several specimens of the semi argentella. You will observe, that in the upper wings of these minute insects, there is a wonderful combination of all the varied shades of molten silver, and burnished gold; they being entirely adorned with plates,. which exhibit in one view the appearance of those costly metals; but by varying the light from the speculum, they