themselves,—nor the silk-worm,—nor the bee, because they have to secrete their own building material, and must be content to use just what they can produce. Men, however, do not create their own building material, but can help themselves to a great variety of it, from various departments of Nature; yet they go on making little cubes of kneaded clay, burning them, and laying them one upon another by millions. If living in damp or windy caves is one kind of barbarism, surely this is another. It might be suitable to the builders of the Babel tower; but it is hardly becoming to the men of a great mechanical age. Without enlarging upon this, or admitting that a brickmaking machinery alters the case while the bricks are laid by hand, I may just point out that the present diversity of construction looks like a promise of progress. We may study the various kinds of houses without particularly liking any, and yet without denying that they afford good suggestion. The most comfortable known dwelling is understood to be the well-constructed log-house, which is built in a week, is free from damp, easily kept clean, cool in summer, and warm in winter, stable and unreverberating, and more durable than the generality of brick dwellings. We cannot have log-houses; but we may take hints from their points of advantage. I am myself far from despising the African and South American houses which are built of clay (we will dismiss the mud) filled into a framework which is removed as the substance dries. We are told that the wooden abodes of Vancouver's Island are fit to live in in a fortnight. The corrugated iron houses which we send out to Australia may be slept in the first night; and they cannot be accused of consisting of too large a number of pieces. They are ugly, however. At present, our greatest advance is building up blocks of stone; and we might rest awhile upon this if there were stone enough cheap enough for everybody. As there is not, we hear with deep interest of inventions by which stone, and even marble, is manufactured. It is no small matter that a great deal of carving of wood and marble is superseded by moulding and casting, whereby much house decoration is brought within the means of others than the wealthy; but it is far more exciting to see how a new generation may discard the barbarism of brick construction, and lodge its humblest members in dwellings which the old world would have classed in the order of palaces.
Every one of these advances will cause a cry on behalf of some working class or another: and on each occasion there will arise fresh proof that civilisation improves the working man's lot more certainly and substantially than any other. Instead of arguing here a matter which always settles itself, I will merely point to the conspicuous instance of agricultural improvement. As the Carolina negro now works the soil with his hoe, and his rude stick of a plough, the British labourer once worked in the field where at present every process is done by machinery. Where every clod was knocked about by the hoe, and every weed pulled up by the hand, and every bean dropped into its hole by human fingers, newly invented implements now do the whole. If the entire process had been foreseen at once, what a clamour there would have been about the fate of the hoe-men and the weeders and the bean setters! Yet, where agriculture is most advanced, the additional labourers required are from two per acre upwards. Instead of surplus labour, we hear now of insufficient numbers and rising wages, as well as of an incessant rise in the quality of the labour. Thus it will be in every department of the arts of life; for new occupation is always created by economy of a lower sort of work. If our Exhibition gives a start to our old civilisation, it will at the same time afford a fresh stimulus to the demand for brains and hands to work our new resources.
ICHNEUMON FLIES AND THEIR PREDATORY LARVÆ.
The entomological family Ichneumonidæ, to which belongs the race of four-winged flies whose larvæ prey upon the larvæ of other insects, has received its name from that of the little ferret-like animal, common in Egypt, which is said to feed upon the eggs of the crocodile. Just as the Egyptian Ichneumon destroys the crocodile in embryo by attacking the egg, so the larvæ of this race of flies destroy vast numbers of insects in their preparatory stages, by consuming the living caterpillar as their natural food, and hence the adoption of the term "Ichneumon " for one of the genera, and "Ichnenmonidæ" for the entomological group which includes this family of insects.
These parasitic flies deposit their eggs on the bodies of caterpillars, piercing the soft skin with a sharp ovipositing instrument with which they are furnished. The tribe of true Ichneumon flies have been popularly termed by French entomologists mouches vibrantes, on account of the continual and rapid vibration of their antennae, and also mouches triples, from the three hair-like appendages or triple tail with which they are furnished. and which is, in fact, the lancing instrument by means of which the skin of caterpillars and the shells of the eggs of certain insects are pierced. The engraving on the next page, which represents one of the largest of the family Ephialtes manifestator, will serve to show the appearance of the triple tail.
These Ichneumons which, in the early stage of their existence, feed upon the flesh of other insects, and which when they attain to their perfect state take only such innocent and delicate food as the honeyed syrup furnished by the nectaries of flowers, belong chiefly to the extensive order Hymenoptera, to which also belong the bee family and a great number of other insects having two pairs of transparent wings; but there is a certain other family of predatory flies, belonging to the order Diptera (comprising two-winged insects), which, though not termed Ichneumons, have yet the same instinct of depositing their ova on the bodies of insects, which those ova, when hatched, are destined to devour. Among these are several Syrphidæ, which deposit eggs on the larvæ of certain bees.
The true Ichneumons, as I have stated above, deposit their eggs on the caterpillars of certain butterflies and moths, and even on the eggs of some of the larger insects of that order, being