IX.—THE EARS AND NOSES OF INSECTS.
Most of us have a vague idea that what we call the 'ear' is only partly concerned with the work of hearing; but only a few know exactly what a complicated organ the ear, as a whole, really is. The external 'ear' only serves as an aid to the collection of sounds, and the real work of hearing is performed by a delicate organ inside the head. Seals, moles, whales, and porpoises, birds, reptiles, and fishes have no visible ear; yet we know that they are not deaf, though in many the hearing must be dull. In all these creatures the sense of hearing lies inside the head.
But the ears of insects must be looked for in strange places indeed, and, when found, they seem to bear no sort of likeness to what most of us call ears. They may be on the antennæ, on the trunk, or on the legs! In the grasshopper, for example (fig. [1]), the ear is placed on the abdomen, just above the base of the great hind-leg, so that this leg must be pulled down before the ear can be seen. When this has been done, there will be found an oval drumhead-like spot (figs. [2] and [3]); this is the outer surface of the ear. If you had sufficient skill to take away this part of the body, so as to show the inside of this drum, you would find two horn-like stalks, to each of which is fastened a small and very delicate flask, with a long neck. This is filled with a clear fluid, and corresponds to a similar structure within our own ears.
In the green grasshoppers—those delightful sprites of hot summer days—'ears' of a precisely similar structure are found on the fore-leg instead of on the body.
In a little gnat-like insect known as Corethra, common in England during the summer months, the 'ear' takes the form of delicate hairs growing out from the body on a stem, like the teeth of a comb; the base of what corresponds to the back of the comb is connected with a delicate nerve, and this, as in the case of the similar nerve in the grasshopper and locust, makes hearing possible.
Only in some ants and bees, and in some mosquitoes, is the organ of hearing placed on the head. We say on, rather than in, the head, because it is formed by a modification of part of the antennæ. A German naturalist, named Mayer, performed an experiment to prove that the hairs on these antennæ can be made to vibrate by means of a tuning-fork. Only those hairs which have to do with the production of sound answered to the notes of the tuning-fork, and these vibrated at the rate of five hundred and twelve vibrations per second. Other hairs vibrated to other notes, which were those of the middle octave of the piano and the next above it. Mayer also found that certain of these vibrations corresponded with the notes produced by the 'song' of the female mosquito. Consequently, when she begins to 'sing,' her tune, like the tuning-fork, sets in motion those hairs on the antennæ of the male which are tuned to these vibrations. Having once found, by the movement of his antennæ, much as a horse moves his ears, from which direction the sound is coming, the male is able to fly at once to his mate. From the accuracy of this flight, Professor Mayer believes that the perception of sound in these little creatures is more highly developed than in any other class of animals.
Fig. 1.—Grasshopper, slightly magnified.
In our illustration some of these curious 'ears' are shown. Fig. [2] shows the ear of the grasshopper magnified. In fig. [3] this is further magnified to show the V-shaped mark which represents the horny stalks to which we referred, seen through the clear membrane of the drum. The dark border (b) around the drum represents a raised ridge. In fig. [4] we have the antennæ of a gnat, some of the hairs of which serve as sound-conductors to delicate nerves lying at their base.
Fig. 2.—Ear of Grasshopper, drum at A, greatly magnified.
Fig. 3.—Drum of Grasshopper's Ear, greatly magnified.
The sense of smell in insects lies mainly in those wonderful organs, the antennæ or 'horns.' Scents of various kinds are perceived either through pits, or through peg- or spike-like teeth filled with fluid. The leaf-like plates of the antennæ of the cockchafer (fig. [5]) have these pits very highly developed. On the outer surface of the first 'antennal' leaf, as also on the edges of the other leaves, only scattered bristles are seen; but on the inner surface of the first and seventh leaves, and on both surfaces of all the other leaves, there are close rows of shallow, irregularly shaped hollows. Their number is enormous—in the males as many as thirty-nine thousand, and, in the female, thirty-five thousand on each antenna. As some of the scent-laden air reaches the surface of these pits, it causes the nerves of smell to be roused, and so guides the beetle to its mate, or to its food, according to the nature of the smell. These pits are so tiny that they cannot be shown on the antennal leaves of the cockchafer shown in fig. [5], but they are there. On fig. [6] a highly magnified section of one of these 'leaves' of the antenna is shown: 'p' is the pit, 'n' is the nerve, and 'S. C.' the sense-bulb of the nerve in which it terminates—the point at which the smell is perceived.
Fig. 4.—Antenna of Gnat, greatly magnified.
Fig. 5.—Antenna of Cockchafer, greatly magnified.
Fig. 6.—Section of "leaf" of Cockchafer's Antenna, greatly magnified.
It has been proved that insects which have lost their antennæ have no sense of smell.
AFLOAT ON THE DOGGER BANK.
A Story of Adventure on the North Sea and in China.
"The donkey-man caught hold of Krüger's tail with both hands."
Fourteen days after leaving Liverpool the Twilight arrived at Port Said, and Fred, Charlie, and Ping Wang at once went ashore. The Pages thoroughly enjoyed their first glimpse of the East, for Ping Wang, knowing the place, took care that they should see everything worth seeing. After sitting for a time in a big café which was crowded with men of almost every European nation, they wandered through the shop district, and out into the Arab portion of the town.
After they had looked at the sights for some little time, Ping Wang suggested that they should have a donkey ride. They had noticed the large, handsome donkeys soon after they landed, but as the passengers from a big P. & O. vessel had come ashore just before they arrived, all the animals were engaged. But when they returned to the busy part of the town they found three donkeys on hire, and the donkey 'boys,' two of whom were elderly men, at once shouted out the names of their animals.
A Port Said donkey sometimes has its name changed three or four times in a year, in consequence of its proprietor's desire that it shall always bear one which is just then popular with Englishmen. You may ride on 'W. G. Grace' in June, and on returning to Port Said in December will discover that the same animal is now called 'Mr. Chamberlain,' or 'Lord Charles Beresford.' The donkeys which Fred, Charlie, and Ping Wang found on hire were named respectively 'Lord Roberts,' 'General Buller,' and 'Krüger.'
Charlie sprang on to 'Lord Roberts's' back; Fred made a rush for 'General Buller,' and left Ping Wang to mount 'Krüger.'
'Let us have a race,' Charlie suggested, when they were getting clear of the crowded narrow streets, and immediately all three urged on their donkeys; but, before they had gone many yards, 'Krüger' began to leave his companions behind.
'This will never do,' Charlie declared, and touched up 'Lord Roberts' with his stick. Fred tried to hurry up 'General Buller.' Neither of the animals, however, appeared to be at all anxious to exert themselves, and they would have lost the race had not the donkey-man, remembering that his English patrons always seemed pleased when 'Krüger' was last, caught hold of 'Krüger's' tail with both hands, and, throwing back his head, pulled as if he were engaged in a tug of war. 'Krüger,' not liking this strain upon his tail, slackened speed and stopped. 'Lord Roberts' and 'General Buller,' evidently fearing that if they continued running they would be treated in the same way as 'Krüger' had been, stopped with such suddenness that Fred was shot over his animal's head into the road, and Charlie only just escaped a similar fate by throwing his arms round his Jenny's neck.
'This is a nice thing!' Fred declared, ruefully, as he pointed to a big tear in his trousers. 'To-day is the first time I have worn this suit.'
Ping Wang condoled with him, but Charlie, who always maintained that his brother thought too much of dress, laughed at his mishap.
'If you had been wearing a serviceable suit like mine,' he said, 'your trousers would not have been torn.'
'May the day never come,' Fred answered, solemnly, 'when I have to take your advice on the matter of dress. And now I think it is about time that we returned to the Twilight.'
'Shall we have another race?' Ping Wang asked eagerly, somewhat disappointed at having been robbed of his victory.
'I've had quite enough racing, thank you,' Fred declared, placing his hand over his knee to conceal the rent in his trousers.
'I haven't,' Charlie joined in. 'Come along, Ping Wang.'
Charlie and Ping Wang whipped up their donkeys, but no sooner had they started than Fred's animal, in spite of its rider's efforts to restrain it, bolted after them, and, overtaking them, ran a dead heat with 'Lord Roberts.' 'Krüger' was last.
When, after a little further exploration of the town, they went back to the Twilight, they were thoroughly delighted to find that she had finished coaling, and that nearly all traces of that unpleasant job had been removed.
They went down to dinner at once, and when they came on deck again they were in the Suez Canal. Fred and Charlie found plenty to interest them in the Canal. They saw several thin brown pariah dogs wandering about the desert in search of food, and once a dead camel came floating by them. Towards evening the Twilight had to anchor for a time, and the three passengers, with the captain's permission, went ashore and gathered flowers and shells to send home.
In the Red Sea there was still more to see. All day long the seagulls—brown with white breasts—hovered around the Twilight. Many other birds came and rested on the ship for hours, and, as the weather was intensely hot, Charlie, Fred, and Ping Wang found it very entertaining to sit quietly in their long chairs and watch their pretty little feathered visitors.