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Show Just HOW the BUTTERFLY HEARS ing the ardent serenade of a would-be wooer. It ia reasonable to conclude that the very similar but more delicate organ in butterflies has a similar simi-lar function, though we can npt teat the matter in the aame manner, but it seems certain that - many butterflies are affected by high, shrill tones, such as that made by rubbing a cork against a wet glass, and that in the Endroaa aurita the female answers a clattering sound made by the male with a fluttering motion of the body and wings. In general, it seems especially the males which are provided with a chirping apparatus. But while the -production of sound is thus shown to be connected with the mating instinct and to form a meana of courtship, thla function is also assisted by sight and smell. An unexpected discovery dis-covery is that organa of hearing are more frequently fre-quently found In butterflies that fly by day than in those that fly by night NUMEROUS interesting experiments have been made with regard to the sensory organs or-gans of insects. In the latest volume. No. 41, of The Zoological Tear Book, published in Berlin, there are reported the results of an extremely ex-tremely extensive study mads by Prof. F. Eggers, concerning the organa of hearing of soma of the butterflies, the spiders, and the moths. These possess certain structures in the last ring of the thorax which have hitherto escaped notice, the significance of which hss been ignored. It now appears that thia structure is a so-eolled tympanal organ, similar to that possessed by crickets and grasshoppers, but much more delicately constructed. construct-ed. The essential part of this organ is an air-filled, air-filled, trachean vesicle or "bladder" (such as is possessed by many winged insects and by some butterflies), which lies very close to two extremely extreme-ly thin portions of the external covering of chitin ; these two attenuated portions of the chitin are known as the true drumhead and the opposite drumhead. The "true" drumhead is so-called because be-cause it ia connected with the delicate nervous apparatus ap-paratus designed to receive the vibrations of sound waves; the opposite drumhead is not thus provided and probably acta merely aa a sort of ' sounding-board to reinforce the vibration The nerve apparatus itself consists of a strand of - connected cells attached to the elastically vibrating vibrat-ing drumhead; this strsnd of cells contains two sensory cells, the delicate projections of which end in the so-called "peg," which is characteristic of what is known as the chordo-tonaj organa. ' That the insect distinguishes sounds through" the tympanal organ has been satisfactorily proved by experimenta with crickets, since it haa been found that the well-known chirping sound uttered by the male attracta only those females in possession of this organ, whereas, when it waa destroyed, the female was incapable of "perceiv- |