They may be known by the large folded front pair of wings, and the two bristle-like appendages at the tail.

QUITTING the Neuroptera, we must give a few lines to another order of insects, the TRICHOPTERA, popularly known by the name of CADDIS-FLIES.

These insects, of which there are many species, are chiefly remarkable in their larval state, on account of the curious portable habitations which they construct. All anglers are familiar with the Caddis, and the singular variety of form and material employed in the construction of its home. Being a soft, white grub, totally unarmed, and presenting a most delicate morsel to every river-fish, the Caddis is forced to conceal itself in some way from its innumerable foes. For this purpose, it builds around itself a nearly cylindrical tube, open at each end, and composed of substances varying according to the locality and the species. Sometimes these tubes are made wholly of short pieces of stick, laid sometimes side by side, and sometimes in a partly spiral form, something like the wires of the submarine telegraph. Sometimes the tubes are made of sand or little stones, while the deserted shells of the planorbis, and other fresh-water shells, are very common materials.

More than once I have known the Caddis to affix living shells to its case, and in consequence to be sadly bewildered when it wanted to move in one direction and the fettered shell tried to move in another. Fragments of reeds, patches of dead leaves, straw, seeds, and all kinds of similar substances, are employed for this purpose by the Caddis. In my own collection, I have several specimens where the creature has made use of the opercula once belonging to dead molluscs, and one instance where the Caddis has pressed into its service the chrysalis of some moth that had fallen into the water. In some species, the shape of the tube is precisely like that of the elephant tusk-shell, described on page 403, and is built up of fine sand. I found great numbers of them in a deserted stone quarry in Wiltshire.

When the larva is about to enter the pupal state, it prepares for the expected change by fixing the tube to some firm object, and spinning a sieve-like net across each extremity, so as to permit water to pass, but to exclude all enemies. There is a regular pattern in this net, and each species seems to have a pattern peculiar to itself. Cases thus prepared may be procured near the beds of streams and rivers, where they may be seen anchored to the submerged plants and stones. The reader will not fail to notice the analogy between the moveable tube of these insects and that of the too common clothes-moth. The word Trichoptera signifies hairy-winged, and is given to these insects in allusion to the soft hairs with which the front pair of wings are usually coated.

We now come to a vast order of insects, technically called the HYMENOPTERA. In these insects the wings are four in number, transparent, membranous, the veins comparatively few, and the hinder pair smaller than the others. Their mouth is furnished with powerful horny jaws, and with a tongue guarded by the modified maxillæ. The females are armed with a many-valved sting or ovipositor. In this enormous order are included all the bees, wasps, and their kin, the great family of saw-flies, the ichneumons, the gall-flies, and the ants, each single family being so large, and presenting so many points of interest, that an entire volume could be devoted to them with great profit. Our space, however, prohibits us from attempting more than a slight sketch of each family, together with descriptions of a few typical species. Without, therefore, enumerating the various arrangements of this large order, or the characteristics on which they are founded, we will proceed at once to the family of the Tenthredinidae, or Saw-flies, the first in Mr. Westwood's system.

In this and the next family, the females are furnished with a peculiar ovipositor. composed of several pieces, and which, though connected with a gland secreting an irritant fluid, are not envenomed as in the bees, wasps, and their kin. All these insects are comprised under the general term of Terebrantia, or borers, and fall easily into two large groups, in one of which the abdomen proceeds directly from the thorax, and in the other is connected with the thorax by means of a footstalk. Each of these groups is further subdivided, as will be seen in the course of the following pages.

The true Saw-flies are known by the curious piece of animal mechanism from which they derive their name. The females of this family are supplied with a pair of horny saws, placed side by side on the lower extremity of the abdomen.

These saws are of various forms, according to the particular species to which they belong, and may be seen even in the dried specimens, the top of their sheath slightly projecting, and their shapes plainly visible after the removal of a portion of the abdomen. When taken from the insect and placed under the microscope, they present a very pretty appearance, owing to the gently-curved ribs with which their sides are strengthened and decorated. The saws act alternately, one being pushed forward as the other is being retracted. Their object is to form a groove in some plant, in which the eggs of the mother insect can be deposited, and wherein they shall find a supply of nourishment in order to enable them to complete their development; for it is a most remarkable fact that, after the egg is deposited in the groove, it rapidly increases in size, obtaining twice its former dimensions.

In the genus Cimbex, of which an example is given in the illustration, the larvæ possess twenty-two feet, and have the power of discharging a translucent greenish fluid

from certain pores placed on the sides of the body just above the spiracles. This feat they can repeat six or seven times in succession. When they have eaten their way to the next stage of existence, they spin a cocoon of a brownish colour and of a stringy, tough consistency, and either suspend it to the branches of the tree on which they have been feeding, or hide it under fallen leaves. In this cocoon they remain for a comparatively short time, and then emerge as perfect insects.

The terrible TURNIP-FLY (Athalia centifolia) belongs to this family. The larva of this species is popularly called the Nigger, on account of its black colour. A species of Athalia may be seen in the engraving on page 463, and is the smallest of the three flying insects at the upper part of the illustration. The larva of this species feeds upon the various cabbages, eating away the whole of the soft green parts of the leaves, and only

rejecting the thick nervures. It makes no cocoon, but retires into the ground, excavates a kind of oval cell, which it lines with a slimy substance, and there awaits its final change.

The well-known black GOOSEBERRY-FLY (Nématus grossulário) is another of the Sawflies. Its larva, so destructive to the fruit, is blackish grey. These tiresome creatures are often seen in great numbers, more than a thousand having been taken on a single gooseberry-bush, and there are two broods in the course of a year. Without going into further details, it is sufficient to say that there is hardly a plant without its especial Saw-fly, and that any one who can discover a really effectual mode of checking their ravages, will confer no slight benefit on mankind.

THE fine insect on the same illustration, which is known by the name of the GIANT ICHNEUMON, is an example of the next family, in which the ovipositor is converted into a gimlet instead of a double saw. With this powerful instrument, the female is enabled to drill holes into living timber for the purpose of depositing the eggs. When they are hatched, the young grubs immediately begin to gnaw their way through the wood, boring it in every direction, and making burrows of no mean size. Those of the present species prefer fir and pine, and I have had specimens of the wood sent to me which have been riddled by the grubs until they looked as if they had harboured a colony of the shipworm. The perfect insects often make their appearance in houses, the larvæ having been concealed in the timbers and rafters ; and I know of one case where a gentleman who had built a wooden garden-house, was sadly annoyed by the multitudes of the Sirex which emerged from the timber. In such cases the insects do not seem to attain their full dimensions, but appear dwarfed and stunted. All wood-boring insects are, however, extremely variable in size.

The next group of the Terebrantia is called Entomophaga, or Insect-eaters, because the greater number of them are parasitic upon other insects, just as the Saw-flies are parasitic upon vegetables. In these insects the ovipositor is furnished with two delicate spiculæ, and the last segments of the abdomen are not formed into a telescope-like tube.

The first family is that of the Cynipidæ, or Gall insects, the creatures by whose means are produced the well-known galls upon various trees, the so-called oak-apple being perhaps the best known, and the Ink-gall (also found on the oak) the most valuable. These Galls are formed by the deposition of an egg in the leaf, branch, stem, twig, or even root of the plant, and its consequent growth. The well-known Bedeguar of the rose, with its soft mossy envelope and delicate green colour, relieved by bright pink, is caused by one of these insects (Cynips rose); and the celebrated Dead Sea-apples are nothing but galls formed by the Cynips insána. The spherical oak-galls, which contain a single insect, and are about the size of a large marble, are closely allied to the true Ink-galls; and if one of these objects be cut with a knife, the action of the astringent juice upon the iron of the blade will produce a kind of ink. The best galls are those which are gathered before the insect makes its escape, as the astringent quality is then more powerful.

The true Ichneumons, of which a specimen is given in the illustration, form a vast group of insects, the British Ichneumonidæ alone numbering many more than a thousand described and acknowledged species. In them the ovipositor is straight, and is employed in inserting the eggs into the bodies of other insects, mostly in their larval state. In some cases, this slender and apparently feeble instrument is able to pierce through solid wood, and is insinuated by a movement exactly like that which is employed by a carpenter when using a bradawl. When not engaged in this work, the ovipositor is protected by two slender sheaths that enclose it on either side.

Were it not for the Ichneumons, our fields and gardens would be hopelessly ravaged by caterpillars and grubs of all kinds, for practical entomologists always find that when they attempt to rear insects from the egg or the larval state, they must count upon losing a very large percentage by the Ichneumons.

Take, for example, three or four caterpillars of the common white cabbage butterfly, place them under water, and open the body from end to end. It will be found that, in

almost every case, the caterpillar bears the seeds of death within its body in the shape of tiny white grubs, like very minute grains of rice. These creatures are the young of an Ichneumon-fly (Microgaster glomerátus), and retain their place within the caterpillar until the time for it to change into the perfect form. They then simultaneously eat their way out of the skin, spin a number of bright yellow silken cocoons, and in process of time change into tiny flies and set out on their destructive mission. The caterpillar never survives their attacks, and is seldom able to move away from the spot whereon it happened to be when the Ichneumons make their escape, the body being enveloped in their yellow cocoons.

All the Ichneumon-flies may be distinguished by their fussy restless movements, as they run up and down any object on which they may settle, and the continual quivering of their antennæ. The two lower figures in the illustration belong to this family, that on the left showing an example of the long ovipositor with which several species are furnished, and the other being given in order to show the wasp-like abdomen and the curled antennæ.

The Rhyssa persuasoria is the largest British Ichneumnon, and is parasitic on Urocerus juvencus, another species of the same genus as that to which the giant Ichneumon belongs. The larva on which it preys bores deep holes in fir-trees, and, in consequence, the Rhyssa may be seen running up and down the trunks in search of some spot where the ovipositor may be introduced so as to lodge in the hidden larva. So deeply does the insect contrive to force its weapon into the wood, that it sometimes is unable to withdraw it, and may be seen hanging dead and dry to the tree in which it has buried the ovipositor too firmly.

PASSING by several families

belonging to this group, we must briefly mention the beautiful RUBY-TAIL FLIES, or CUCKOO FLIES, so plentiful in summer about old walls and similar localitics. These are distinguished by the fact that, in the females, the last segments of the abdomen are formed into a telescopic tube, which can be projected or retracted at pleasure, and is furnished with a minute sting. These are, perhaps, the most brilliant in colour of any British insect, and are veritable humming birds of the insect tribes, their bodies literally flashing with ruby, sapphire, and emerald, as they flit restlessly in the sunbeams. They are parasitic insects, and haunt the walls for the purpose of depositing their eggs in the larvæ of sundry solitary bees and wasps.

IN the next great division of Hymenopterous insects, the ovipositor of the female is changed into a sharply pointed weapon, popularly called a sting, and connected with a gland in which is secreted a poison closely analogous to that which envenoms a serpent's tooth. These are again divided into the Insectívora, or those which have fore-wings not folded, and the larvæ solitary and feeding on other insects; the Sodáles, where the forewings are not folded, and the larvæ are social; and the Diplóptera, where the fore-wings are folded, and the larvæ (in the social species) inclosed in separate cells.

The first of these sections comprises all those curious and interesting insects known popularly by the names of Sand Wasps and Wood Wasps. These creatures are in the

498

THE BURROWING WASPS.

habit of making burrows into the ground or in posts, and placing therein their eggs, together with the bodies of other insects which are destined to serve as food for the future progeny. Spiders are sometimes captured and immured for this purpose. In many instances the captured insects are stung to death before they are placed in the burrow, but it is often found that they only receive a wound sufficient to paralyse them, so that they lead a semi-torpid life until they are killed and eaten by the young grub. Two of these Sand Wasps are given in the illustration. That on the left is one of the woodborers, drilling its burrow into posts, palings, and similar substances, and feeds its young with the larvæ of one of the leaf-rolling caterpillars that lives in the oak, and is scientifically known by the name of Tortrix chlorána. It also employs for this purpose several two-winged insects. One species of these burrowing wasps prefers the well-known cuckoo-spit insect for this purpose (Aphróphora spumária), pulling it out of its frothy bed by means of its long legs.

The right-hand figure represents a species that is in the habit of provisioning its urrow with the hive-bee, which it contrives to master in spite of the formidable weapon possessed by its victim, and then murders or paralyses by means of its sting. M. Latreille mentioned that he saw from fifty to sixty of these insects busily engaged in burrowing into a sandbank not more than forty yards long; and as each female lays five or six eggs, and deposits a bee with each egg, the havoc made among the hives is by no means inconsiderable.

IN the accompanying illustration is shown a Brazilian species, belonging to a genus which is represented in England by more than twenty species. In these insects the legs are very long and spider-like, enabling their owners to run about among grass with great vivacity, their wings quivering all the while with violent agitation. Some of the species are in the habit of catching spiders, and provisioning the burrows with them. It is worthy of notice, that the largest specimens of Hymenoptera are to be found in exotic insects belonging to this family, the genus Pepsis being most remarkable for the great dimensions of its members.

The right-hand figure represents an insect which, though common in Southern Europe, has not yet been satisfactorily proved to be an inhabitant of England. Judging by the habits of those species which have been studied, the whole of the family to which it belongs are sand-burrowers, and seem to be cruelly predacious, mastering insects of considerable size, and dragging them into their burrows. One of these insects (Scólia bicincta) has been known to capture and inter a large locust, the tunnel being some eighteen inches in depth and very wide at the mouth.