the entire order of Neuroptera has antennal ears, and should therefore in this respect be classed with Lepidoptera. [17] Consult Furneaux, _Life in Ponds and Streams_, p. 325. In grasshoppers and crickets the ears are situated in the anterior pairs of legs. If the tibia of a grasshopper's anterior leg be examined, two (one before and one behind) shining, oval, membranous disks, surrounded by a marginal ridge, will be at once observed. These are the tympana or ear-drums of the ear of that leg. Where the trachea, or air-tube, enters the tibia it becomes enlarged and divides into two channels; these two channels unite again lower down in the shaft of the tibia. The tracheæ of non-stridulating grylli are much smaller than those of sound-producing grasshoppers. The same may be said of the tibial air-tubes of the so-called dumb crickets. In grasshoppers and crickets the ear-drums lie bathed in air on both sides--the open air on the external side and the air of the air-tube, or trachea, on the inside. Lubbock calls attention to the fact that "the trachea acts like the Eustachian tube in our own ear; it maintains an equilibrium of pressure on each side of the tympanum, and enables it freely to transmit atmospheric vibrations." In grasshoppers the auditory nerve, after entering the tibia, divides into two branches, one forming the supratympanal ganglion, the other descending to the tympanum and forming a ganglion known as Siebold's organ. This last-mentioned ganglion is strikingly like the organ of Corti in our own ear, and undoubtedly serves a like purpose in the phenomenon of audition. The organ of Corti is composed of some four thousand delicate vesicles, graduated in size, each one of which vibrates in unison with some particular number of sound vibrations. The organ of Siebold in the grasshopper's ear begins with vesicles, of which a few of the first are nearly equal in size; these vesicles then regularly diminish in size to the end of the series. Each of these vesicles contains an auditory rod, and is in communication with the auditory nerve through a delicate nerve-fibril. I have observed that each of these nerve-fibrils swells into a minute ganglion immediately after leaving its particular vesicle; the function of these ganglia is, I take it, to strengthen and reënforce nerve-energy. No other observer mentions these ganglia, as far as I have been able to determine; they may have been absent, however, in the specimens studied by others, yet in the specimens studied by myself--the "red-legged locust" (_Melanoplus femur-rubrum_, Comstock)[18] and the "meadow grasshopper" (_Xiphidium_), they were always present. [18] Consult Comstock, _Manual for the Study of Insects_, p. 110. That grasshoppers, locusts, and crickets can hear, no one who has observed these creatures during the mating season will for one instant deny; they hear readily and well, for in most of them the sense of hearing is remarkably acute.