know that, however careful we may be in inserting a cork into a glass, the mercury with which it is filled is not sheltered from the action of the air, which weighs upon the cork; we know that the air passes through, and acts upon the mercury in the tube. The air can also, in the same way, penetrate through the obstruction of a gall of wood, though it have no perceptible opening or crack; but the air cannot pass in this manner so readily through the skins and mem'branes of animals. In order to see the interior of the cavity of an animal-gall, Réaumur opened several, either with a razor or a pair of scissors; the opcration, however, cannot fail to be painful to the cow, and consequently it renders it impatient under the process. The grub being confined in a tolerably large fistulous ulcer, a part of the cavity must necessarily be filled with pus or matter. The bump is a sort of cautery, which has been opened by the insect, as issues are made by caustic the grub occupies this issue, and prevents it from closing. If the pus or matter which is in the cavity, and that which is daily added to it, had no means of escaping, each tumour would become a considerable abscess, in which the grub would perish: but the hole of the bump, which admits the entrance of the air, permits the pus or matter to escape; that pus frequently matts the hair together which are above the small holes, and this drying round the holes acquires a consistency, and forms in the interior of the opening a kind of ring. This matter appears to be the only aliment allowed for the grub, for there is no appearance that it lives, like the grubs of fleshflies, upon putrescent meat. Mandibles, indeed, similar to those with which other grubs break their food, are altogether wanting. A beast which has thirty, forty, or more of these bumps upon its back, would be in a condition of great pain and suffering, terrible indeed in the extreme, if its flesh were torn and devoured by as many large grubs; but there is every appearance that they do not at all afflict, or only afflict it with little pain. For this reason cattle most covered with bumps are not considered by the farmer as injured by the presence of the fly, which generally selects those in the best condition. A fly, evidently of the same family with the preceding, is described in Bruce's Travels, under the name of zimb, as burrowing during its grub state in the hides of the elephant, the rhinoceros, the camel, and cattle. "It resembles," he says, "the gad-fly in England, its motion being more sudden and rapid than that of a bee. There is something peculiar in the sound or buzzing of this insect; it is a jarring noise together with a humming, which as soon as it is heard all the cattle forsake their food and run wildly about the plain, till they die, worn out with fatigue, fright, and hunger. I have found," he adds, some of these tubercles upon almost every elephant and rhinoceros that I have seen, and attribute them to this cause. When the camel is attacked by this fly, his body, head, and legs break out into large bosses, which swell, break, and putrefy, to the certain destruction of the creature." * That camels die under such symptoms, we do not doubt; but we should not, without more minutely-accurate observation, trace all this to the breeze-fly. MM. Humboldt and Bonpland discovered, in South America, a species, probably of the same genus, which attacks man himself. The perfect insect is about the size of our common house-fly, (Musca domestica), and the bump formed by the grub, which is usually on the belly, is similar to that caused by the ox-breeze-fly. It requires six months to come to maturity, and if it is irritated it eats * Bruce's Travels, i. 5, and v. 191. deeper into the flesh, sometimes causing fatal inflammations. GRUB PARASITE IN THE SNAIL. During the summer of 1829, we discovered in the hole of a garden-post, at Blackheath, one of the larger grey snail shells (Helir aspersa, MULLER,) with three white soft-bodied grubs, burrowing in the body of the snail. They evidently, from their appearance, belonged to some species of beetle, and we carefully preserved them in order to watch their economy. It appeared to us that they had attacked the snail in its strong hold, while it was laid up torpid for the winter; for more than half of the body was already devoured. They constructed for themselves little cells attached to the inside of the shell, and composed of a sort of fibrous matter, having no distant resemblance to shag tobacco, both in form and smell, and which could be nothing else than the remains of the snail's body. Soon after we took them, appearing to have devoured all that remained of the poor snail, we furnished them with another, which they devoured in the same manner. They formed a cocoon of the same fibrous materials during the autumn, and in the end of October appeared in their perfect form, turning out to be the Drilus flavescens, the grub of which was first discovered in France in 1824. The time of their appearance, it may be remarked, coincides with the period when snails become torpid.* In the following autumn we found a shell of the same species with a small pupă-shaped egg deposited on the lid. From this a caterpillar was hatched, which subsequently devoured the snail, spun a cocoon within the shell, and was transformed into a small moth (of which we have not ascertained the species) in the spring of 1830. *J. R. 417 THE subject of Insect Architecture, to which this volume is devoted, forms only one division, though a most interesting and important one, of that branch of natural history which relates to insects. It presents some of the most striking views of their economy; and, as we have endeavoured to render the examples of extraordinary instinct with which it abounds obvious and familiar to every reader, it precedes somewhat naturally a more minute account of the physiological part of the science of Entomology, and of the benefits and injuries to man produced by insects in the respective stages of their existence. The present volume is complete in itself; but the subject of Insects is continued in a second volume, entitled "INSECT TRANSFORMATIONS. 12 Exterior wall of mason-bee's nest 13 Cells of mason-bee's nest 14 Varieties in cells of mason-bee's nest, three figures 15 Mason-bee and nest. 16 Cell of mining-bee 17 Nests of carpenter-bees, four figures 18 Carpenter-bee. ib. 19 Teeth of carpenter-bee, magnified ib. 20 Nests of carpenter-wasps, two figures 53 22 Cocoon of a carpenter-wasp 21 Carpenter-wasp 23 Rose-leaf-cutter bees, and nest lined with rose-leaves ib. ib. 61 30 Portion of external crust of social-wasp's nest 35 Part of a honeycomb, and bees at work 38 Structure of the legs of the bee for carrying propolis, &c. 39 Curtain of wax-workers secreting wax 77 ib. 80 82 83 88 89 103 104 110 114 40 Wax-worker laying the foundation of the first cell 117 119 42 Arrangement of cells of hive-bees 122 43 Foundation-wall enlarged and the cells commenced 46 Ovipositor of saw-fly protruded from its sheath, magnified |