affected as well as the stem. Fortunately for the gardener, who hates thistles, even though he should be a Scotchman, as is so often the case with skilled gardeners, the larva of the Cleonus feeds on the juices of the plant at the expense of its life, so that the thistle dies just before the seed is developed, and a further extension of the plant is thereby prevented.

THERE are also gall-making insects among the Diptera. Such, for example, is the THISTLE-GALL FLY (Urophora Cardui), which produces large and hard woody galls upon the thistle, as well as several species of the larger genus Tephritis, some species of which live in the parts of fructification of several flowers, the common dandelion being infested by them.

WE may now describe, at fuller length than has hitherto been done, another group of insects, which live between the membranes of leaves, and which belong to different orders.

If the reader will carefully examine the leaves of any rosetree which grows in the open air, he will certainly remark that many of them are notable for certain curious markings, which look something like the rivers in a map, and which traverse the

leaf in various ways. They all, however, agree in one point namely, their gradual and regular increase in diameter. At their origin, they are so small that the finest thread could hardly pass through them, but in proportion as they increase in length they increase in width, so that at their termination they are sometimes the twelfth of an inch in width.

These marks are the tracks made by very small larvæ, which live between the membranes of the leaves, and feed upon the parenchyma, or soft substance which lies between the two membranes. They follow no rule in their meanderings, but traverse the leaf in a variety of ways. Sometimes they never leave the edge, but follow every little serration of the leaf with perfect accuracy. Sometimes they form a kind of spiral, and sometimes they wander irregularly over the whole leaf. Generally, the insect does not cross the track which it has once made, being diverted from doing so by some wonderful instinct. There are instances, however, where the insect has crossed its own track, not only once, but several times.

If the little gallery be opened at the widest extremity, one of three things will be found. Sometimes there is a tiny white grub, very much resembling the larva of certain beetles, and having the rings which represent the thorax rather wider than those which will afterwards be developed into the abdomen. the little creature is able to live between the membranes of a leaf so thin as that of the rose or oak, it is evident, to the most superficial observer, that the insect which will be developed from it must be of very minute dimensions.

As

The larva of all winged insects is very large in proportion to the same insects when they have obtained their perfect form, much of the substance being taken up by the wings. As a natural consequence, it follows that the larger the wings, the larger must be the grub, the size of the body being quite a secondary consideration. In the present case, the larva which we are supposed to examine belong to the lepidopterous order, in all of which insects the wings, when present at all, are of great comparative size. If, then, the full-grown larva is so small that it can lie concealed between the membranes of a leaf without causing any conspicuous alteration in its outline, it is evident that the perfect insect must be of almost microscopical minuteness. Accordingly, it has been found that the little moths which

have been bred from such caterpillars are so small that they have almost escaped observation until comparatively late years.

How small these insects are may be imagined from the fact that many species of the Microlepidoptera, as they are fitly named, do not occupy, even with their wings spread, a space larger than is taken up by the capital letter at the beginning of this sentence. To "set" these tiny creatures is necessarily an extremely difficult task, and cannot be accomplished by the ordinary plan of running a pin through the thorax, and extending the wings on the "setting-board." The only method of displaying them is to set them on white cardboard by means of gum, which is strengthened by many entomologists with various substances. A sheet of cardboard covered with specimens of Microlepidoptera neatly set is a very pretty sight, but needs the aid of the microscope before it can be perfectly seen.

Even to the unaided eye, the tiny moths are seen to be beautifully decorated, their wings gleaming in favourable lights like the throat of the humming-bird. But when placed under the microscope, especially if it be furnished with a binocular tube, and illuminated by a suitable light, the wings are positively dazzling in their brightness, and hues that formerly seemed to be but dun and bronze or brown, suddenly flash out into gold and emerald, each scale distinct and shining as if of burnished metal.

Sometimes, when opening the extremity of the leafy tunnel, we find a tiny chrysalis lying in the little chamber, and awaiting the time for the shell to burst and the perfect insect to emerge. Later in the year, we shall find neither larva nor pupa, but shall see a little hole in the leafy chamber, from which issues the shattered end of an empty chrysalis-shell, showing that the moth has made its escape into the outer air.

Two examples of other mined leaves may be seen upon the illustration, both drawn from the actual object. The specimen in the right-hand upper corner was taken from the bramble, and has been mined by the larva of a little moth called Nepticula anomella. It is a very pretty little creature, though its hues are not brilliant without the aid of the microscope. The upper wings are brown, but their tips are beautifully coloured with. bright chestnut. The lower wings are pale grey, without any of the brilliancy that distinguishes the upper pair. They possess,

however, a compensating beauty in the long, feathery fringe with which they are edged, and which, when subjected to the microscope, is seen to consist of the ordinary scales of the wings exceedingly developed both in length and width.

The leaves on the left hand were taken from the garden-rose, and have been mined by the larva of another species of the same genus, Nepticula aurella.

This beautiful little moth derives its specific name from the peculiar colouring of the upper wings, which are bright chestnut, relieved by a broad band of gold across their centre. The tips of these wings are fringed, and the lower pair are nearly white, and edged with a fringe similar to that which has already been described.

As a general rule, the leaf-mining caterpillars are solitary, and if even two or three are found in the same leaf, each leads an isolated life, and does not inhabit the same burrow as its neighbour. There are, however, exceptions to this rule, as to most others, and certain species of leaf-miners inhabiting the henbane, live harmoniously together between the membranes of the same leaf. They are larger than the ordinary species, and are remarkable for their power of burrowing into a fresh leaf when ejected from their former habitation, a power which does not seem to belong to the caterpillars of the Microlepidoptera.

As the meandering tracks of the Microlepidoptera upon the leaves of various plants are very similar in general aspect, I have caused figures of common leaf-rollers to be inserted in the illustration. If the reader will turn to pages 294-298, he will see an account of certain moths whose larvæ roll up the leaves in which they reside. The lilac-leaf on the left hand of the illustration has been rolled up by the larva of a moth named Gracillaria syringella, the generic title being given to it on account of its graceful form, and the specific name because it is fond of frequenting the syringa shrub. The larva is shown just below, of its natural size, and the hole through which the perfect insect has escaped can be seen upon the rolled portion of the leaf.

On page 247 may be seen an account of the manner in which the larva performs a task so apparently impossible as rolling up

a leaf of such great comparative size. When the little caterpillar is contrasted with the leaf on which it is at work, the contrast is almost ludicrous, for it seems nearly as impossible for so little a creature to roll up so large a leaf as for a man to roll up one of the armour-plates of an iron-clad ship. The manner by which this task is achieved is described on the abovementioned page, and the reader will be the better able to understand the description if he compares it with the illustration.

The moth which has inhabited this leaf is called Gracillaria semifascia.

To return to our leaf-miners.

Although the greater number of these insects belong to the lepidoptera, the rule is by no means an universal one. Many beetles are thus parasitic within the leaves of plants, and, as a general rule, they belong to the family of Curculionidæ, or weevils. There are also several species of dipterous insects which have this habit, among which may be named the CHRYSANTHEMUM FLY (Tephritis artemisia), which burrows into the leaves of the flower. There is also a genus of flies called Phytomyza, i. e. Plant-sucker, the different species of which select particular plants and burrow between the membranes of their leaves. The holly, for example, is infested by one species, the honeysuckle by another, and the common hart's tongue by a third.

WE must now glance at a few of the insects that are parasitic upon other animals. Their numbers are very great, but we must restrict ourselves to those which construct some sort of a habitation.

The only insect which can be said to be parasitic on man, and at the same time to form a habitation, is the celebrated CHIGOE (Pulex penetrans), otherwise called the JIGGER, or EARTH FLY. This terrible pest is a native of Southern America and the West Indian islands, and is too well known, especially by the negroes and natives.

This insect, which is closely allied to the common flea, and much resembles it in general appearance, contrives to hide itself under the nails of the fingers or toes, usually the latter. Having gained this point of vantage, it proceeds very gradually to make