rest, in the Social, but hooked in the Solitary group, and furnishes a most useful aid in classification. The front of the scape is yellow, as already noticed, in all the sexes of the tree-wasps, and in the males of the ground-wasps. It is important to recollect this, as well as the number of the joints, and the fact of the terminal joint being hooked in the males of the Solitary group.

A longitudinal section of the antennæ of the hornet discloses a series of chambers jointed together. The central space, according to Mr. Newport's description of the antennæ of Ichneumon Atropos, is occupied by a nervous filament, and copiously supplied with a limpid fluid. On either side of this, in the hornet, is a trachea, contracted at the joints, but swelling out in the interspaces, and giving origin to little air tubes which ramify over the interior of the horny covering. This covering is composed of fibres, forcibly recalling the appearance and arrangement of the enamel fibres of the teeth, radiating from the long axis of the antenna, presenting a rough surface externally. A longitudinal section of one of these antennæ, under polarized light, is an object of exceeding beauty.

Popularly the antennæ are known as the insect's feelers, and certainly one of their uses is to examine by touch anything presented to them. If we confine one of the Orthoptera, a cricket or grasshopper, for instance, with its fine, long, antennæ, in a box with a glass lid, we may easily satisfy ourselves on this point. But they are not the only organs of touch, as the palpi of the mouth share this sense with them; nor are their functions limited to the

exercise of this faculty. Doubtless the plumes of the gnat, the leaves of the cockchafer, the beaded filaments of the wasp, and the other countless forms which the antennæ assume in different tribes, have a direct relation to the several habits of the insects which wear them. But, besides all special adaptations, the proper function of the antennæ seems to be that of an instrument of communication in the social tribes, and of an organ of hearing in insects generally.*

The first of these functions has been assigned to these organs by the common consent of all naturalists. What form the communication takes to become intelligible cannot be known, but by means of these little jointed threads, a kind of freemasonry is maintained among the members of a colony, and such a fact as the presence of the queen is transmitted, even through a grating, with as much accuracy as along the telegraphic wires. Ants and bees seem to converse, and call for assistance, by contact of their antennæ, just as the deaf and dumb do by motion or contact of their hands. Wasps, which are less sociable among themselves, and work singly, are perhaps less demonstrative in this way than bees and ants, and exhibit less of this interchange of feelings. But they have means of telling one another what is going on, and very accurately, too, if the curious observation that a wasps'-nest may be attacked with impunity if the outsiders be kept from

*See Newport, On the Use of the Antennæ of Insects, Transactions of the Entomological Society of London,' Vol. II, p. 229. 1837-40.

communicating with the wasps inside the nest be

correct.

With reference to the sense of hearing, one reason for regarding the antennæ as equivalent to the ears of the higher animals is that no other organ has been discovered in insects to which this faculty can be assigned, though it is quite certain, from observation, that insects do not only hear, but make noises with the intention of being heard. As we rise in the scale of Creation, where distinct organs of hearing do appear, they are found close to, and supplied by the same nerves as the antennæ. The hard horny covering of these organs makes them, in the wasp at least, ill adapted for instruments of touch, but in that measure fitted to receive and transmit vibrations of sound.* And in their general structure we may perceive a close analogy to the loose chain of earbones of mammalia, or to the bony needle which in birds performs the same office of transmitting vibrations from the membrana tympani to the auditory

nerve.

Those who have tried most experiments are most alive to the sources of fallacy which vitiate the conclusions from them. We know, from the effects of accident or disease in ourselves, how very small a portion of an organ, how seemingly imperfect an ear, may suffice to carry on its duties. And we know how very little is to be based on the actions of a creature frightened and excited by such mutilation as would be necessary to destroy completely any organ of special sense with all its means of external

* See on this subject Rymer Jones, General Outline of the Animal Kingdom,' 8vo, 1841, p. 275.

communication. Experiments on the perception of sound are singularly open to such objections, and I will not build on any conclusions from them. The proof from comparative anatomy, and from the fact that an instrument shaped in the form of the wasp's antennæ is a very good means of collecting and conveying sound to the point where it can be appreciated, seems to me the best proof we are likely to get that the antennæ of wasps are really their ears.

The various forms which the corona, the little yellow patch which lies between the origin of the antennæ, presents have been already fully described in pointing out the distinctions between the several species. The external figure of the clypeus is less varied. This is the broad yellow shield on which wasps wear the characteristic devices of the different species. It is of an elliptic form above, with occasionally a notch in the middle line. As the sides diverge they come into contact with the lower limb of the compound eyes. The outline is completed below by two straight lines converging to a point, more or less truncated in different species, corresponding to the commissure of the mandibles. The clypeus gives form and width to the face, and protects the soft parts of the mouth which lie immediately behind and beneath it.

The structure of the mouth has been made the basis of one system of classification of insects. But, as these parts are not as open to common observation as the wings, the system of Fabricius has been superseded by that of Linnæus, which supplies much more

readily available distinctions. Still, these parts of the mouth will repay a careful study, as well on account of their physiological importance, as for the sake of the unerring differential characters which scientific examination finds in them.

The mouth of the Wasp, and of the Vespa in particular, furnishes a very good illustration of the mandibulate or masticating form of the organ, where no single part is enlarged or diminished very disproportionately to the rest. It is very difficult to make a symmetrical microscopic preparation of the whole oral apparatus, as the parts are of such different degrees of thickness and hardness, and require such different modes of treatment to show them to the best advantage. But they may be seen in detail, and their description may be followed with the greatest ease, if they are merely loosely spread out on a slide with a little glycerine.

The mandibulate form of mouth, as displayed in our wasps, is made up of the following parts. There is an upper lip, the labrum, which is a simple scale having a vertical plane of movement and a lower lip, the labium, which has a corresponding direction of movement, but is of a more complex structure.

Fig. 1.-Diagram of the several parts of the mouth of the wasp.

a, labium with the four-lobed tongue and the two labial palpi.

b, maxilla of one side, the basilar portions bearing at one end the cardo, at the other the hairy galea and the maxillary palpus.

c, labrum.

d, mandible of one side.