Anyone who has entered a wood where thousands of the seventeen-year cicadas were hatching has never forgotten it. A threshing machine, or a gigantic frog chorus, is a fair comparison, and when a branch loaded with these insects is shaken, the sound rises to a shrill screech or scream. This noise is supposed--in fact is definitely known--to attract the female insect, and although there may be in it some tender notes which we fail to distinguish, yet let us hope that the absence of any highly organised auditory organ may result in reducing the effect of a steam-engine whistle to an agreeable whisper! It is thought that the vibrations are felt rather than heard, in the sense that we use the word "hear"; if one has ever had a cicada _zizz_ in one's hand, the electrical shocks which seem to go up the arm help the belief in this idea. To many of us the song of the cicada--softened by distance--will ever be pleasant on account of its associations. When one attempts to picture a hot August day in a hay-field or along a dusty road, the drowsy _zee-ing_ of this insect, growing louder and more accelerated and then as gradually dying away, is a focus for the mind's eye, around which the other details instantly group themselves. The apparatus for producing this sound is one of the most complex in all the animal kingdom. In brief, it consists of two external doors, capable of being partly opened, and three internal membranes, to one of which is attached a vibrating muscle, which, put in motion, sets all the others vibrating in unison. We attach a great deal of importance to the fact of being educated to the appreciation of the highest class of music. We applaud our Paderewski, and year after year are awed and delighted with wonderful operatic music, yet seldom is the _limitation_ of human perception of musical sounds considered. If we wish to appreciate the limits within which the human ear is capable of distinguishing sounds, we should sit down in a meadow, some hot midsummer day, and listen to the subdued running murmur of the myriads of insects. Many are very distinct to our ears and we have little trouble in tracing them to their source. Such are crickets and grasshoppers, which fiddle and rasp their roughened hind legs against their wings. Some butterflies have the power of making a sharp crackling sound by means of hooks on the wings. The katydid, so annoying to some in its persistent ditty, so full of reminiscences to others of us, is a large, green, fiddling grasshopper.