have several times surprised the Savoyard beetle (Anobium tesselatum, FABR.) beating with redoubled strokes with its head upon the ceiling*" He pretends not to decide whether it was to knock out a cavity for its eggs, or a call to its mate.

Latreille says, the male and the female (Anobia), at the period of pairing, strike many times successively and rapidly with their mandibles the wainscot where they are placed, and mutually answer each other's signal, and such is the cause of the ominous ticking t. He observed an instance of this in the striated timber beetle (Anobium striatum), which, upon striking with its mandibles on the outside of a pile of wood, was answered from within.

We have ourselves observed the clicking made by a beetle (Anobium pertinax), more common, perhaps,

Several species of death-watch beetles greatly magnified. a, Anobium tesselatum. b, Anobium striatum. c, Anobium pertinax.

than the preceding, in the holes of old wood, and have heard it more frequently in the night than the day. It moves its head up and down like a pendulum when it clicks, but we could not be certain whether

* Hist. Nat. des Insectes, iii. 123, ed. 1830.
+ Règne Animal, iv. 484, ed. 1829.

we saw it strike the wood. In the case of the timber-louse (Atropos pulsatorius, STEPHENS), the insect certainly strikes the object; for in consequence of the softness of its body, it could not otherwise produce the clicking, which is much quicker, and not so loud as that of the beetles. We have even distinguished this sound to be much less perceptible when the insect was, as it often is, in a collection of dried plants than when on an old book or a drawer*.

These are only a few of the more remarkable sounds produced by insects; but it is highly probable, as we have already hinted, that these tiny creatures emit many sounds altogether imperceptible to us,an opinion which is strikingly corroborated by the experiments of Wollaston. It is well known that persons affected with slight deafness hear sharp sounds much better than those which are grave and low, being able to distinguish the voices of women and children, in consequence of their acuteness, much better than the lower tones of men's voices. This fact, indeed, is practically acted upon by those accustomed to converse with persons hard of hearing, in which case they use a more shrill, rather than a louder tone of voice than common. Many persons who never felt any defect in their hearing cannot hear certain sounds which others perceive distinctly; and this partial deafness may be artificially produced by shutting the mouth and nose, and then exhausting the air in the Eustachian tube by expanding the chest in a forcible attempt to take breath. When this is done so that the exhaustion of the air behind the drum of the ear is as complete as possible, the external air is felt strongly and even painfully pressing on the drum, in which case the ear becomes insensible to low sounds, though shrill sounds are * J. R.

as readily perceived as before. After the ear is brought into this state it will remain so for some time, without continuing the painful effort to take breath, for, by suddenly discontinuing the effort, the end of the tube will close like a valve, and prevent the air from getting into the drum. The act of swallowing, however, will open the closed tube, and restore the ear to its wonted feeling.

While the ear is exhausted of its internal air, if we attempt to listen to the sound of a carriage passing in the street, the rumbling noise cannot be heard, though the rattle of a chain or a loose screw remains as easily heard as before. At a concert the experiment has a singular effect. As none of the sharper sounds are lost, and the great mass of the louder sounds are suppressed, the shriller ones are consequently so much the more distinctly heard, even to the rattling of the keys of a bad instrument, or the scraping of cat-gut unskilfully touched. In the natural healthy state of the ear, there does not seem to be any strict limit to our power of perceiving grave sounds; but if, on the contrary, we turn our attention to the other extremity of the scale, and with a series of pipes, exceeding each other in sharpness, we examine the effects of them in succession, upon the ears of any considerable number of persons, we shall find a very distinct and striking difference between the hearing of different individuals, whose ears are in other respects perfect. The suddenness of the transition from perfect hearing to total want of perception, occasions a degree of surprise, which renders an experiment, with a series of small pipes, among several persons, rather amusing. Those who enjoy a temporary triumph, from hearing notes inaudible to others, are often compelled, in their turn, to acknowledge to how short a distance their superiority extends. Dr. Wollaston accord

ingly found that one of his friends was quite insensible to the sound of a small organ-pipe, which was far within the limits of his own hearing. He also remembers a female relation to have said that she never could hear the crink of the hedge-cricket. Two ladies of his acquaintance told him that their father could never hear the chirping of the housesparrow, and this is the lowest limit to acute hearing which he met with, and he supposes it to be very uncommon; deafness, even to the sound of the house-cricket, is not usual, while it is by no means rare to find people who are insensible to the shrill squeak of the bat.

The range of human hearing comprised between the lowest notes of the organ, and the highest known sound of insects, includes more than nine octaves, the whole of which are distinctly perceptible by most ears. But "since there is nothing," Dr. Wollaston concludes, "in the constitution of the atmosphere to prevent vibrations much more frequent than any of which we are conscious, we may imagine that animals like the crickets (Grylli), whose powers appear to commence nearly where ours terminate, may have the faculty of hearing still sharper sounds, which at present we do not know to exist; and that there may be other insects, hearing nothing in common with us, but endowed with a power of exciting, and a sense that perceives, vibrations indeed of the same nature as those which constitute our ordinary sounds, but so remote, that the animals who perceive them may be said to possess another sense, agreeing with our own solely in the medium by which it is excited, and possibly wholly unaffected by the slower vibrations of which we are sensible *.

* Dr. Wollaston in Phil. Trans. for 1820, p. 314.

ORGAN OF HEARING IN INSECTS.

LEAVING insects for a moment out of consideration, we find a much greater difference in the form and structure of the ears, than of the eyes, of other animals. The eyes are always placed in nearly the same part of the head, and consist of a transparent portion more or less complicated, and a nervous expansion for receiving the visual image. This uniformity, however, does not hold in the case of ears, for though their situation is as constantly the same as the eyes, their form is exceedingly varied. The opening of the ear, for example, is admirably contrived. "In the owl that perches on a tree," to use the words of Grew, "and hearkens after the prey beneath her, it is produced farther out above than it is below, for the better reception of the least sound. But in a fox, that scouteth underneath the prey at roost, it is for the same reason produced farther out below. In the polecat, which hearkens straight forward, it is produced behind, for the taking of a forward sound. Whereas in a hare, which is very quick of hearing, and thinks of nothing but being pursued, it is supplied with a bony tube, which as a natural otocoustick (ear-trumpet) is so directed backward, as to receive the smallest and most distant sound that comes behind her*.' The outer ears also of hounds, swine, and other animals designed to hear low sounds, are either pendulous or moveable, to compensate for their difficulty of moving the head; for were their ears not so constructed, hogs while eagerly digging for roots, and hounds when keenly pursuing their game by the scent, might fall into danger, which their hanging ears readily intimate by catching the lowest sounds that float along the ground.

*Cosmologia Sacra, i, 5.