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HARDWICKE'S SCIENCE-GOSSIP. 



elytra is to shut them. Each tooth, more particularly 

 those occupying the central portion of the ridge, 

 that is the largest teeth, have projections on each side ; 

 these projections would thus be the most elastic 

 portions, and would of course vibrate the most freely, 

 I have met with a few statements as to the method 

 by which the sound is produced. Dr. Carpenter, in 

 the "Microscope," says "the sound-producing 

 apparatus consists of the ' tympanum ' or drum, 

 which is a space on each of the upper wings, scarcely 

 crossed by veins, but bounded externally by a large 

 dark vein, provided with three or four longitudinal 

 ridges, and of the ' file ' or ' bow ' which is a trans- 

 verse horny ridge in front of the tympanum, furnished 

 with numerous teeth, and it is believed that the sound 

 is produced by the rubbing of the two bows across 

 each other, whilst its intensity is increased by the 

 sound-board action of the tympanum." Dr. Brewer, 

 in his treatise on " Sound," says " the merry ' hearth 

 song ' is produced by the attrition of the anterior 

 pair of wings against each other. One of the wing 

 cases has its edge notched or indented like a file or 

 delicate saw, and this shard is made to pass over the 

 shard or sheath of the opposite wing. The sound 

 thus produced is augmented by resonance from a 

 certain part of the wings, surrounded by strong 

 nervures, which stretch the thin membranes so 

 tightly that they act like a drum head." Whilst in 

 a supplement or notes to a Natural History of Insects 

 by Cuvier, it is stated "when he wishes to make 

 himself heard he raises his elytra so as to form an 

 acute angle with his body. Then he rubs one against 

 the other with a horizontal and very quick motion. 

 The elytra of the male are of a drier and more elastic 

 nature, which renders them fit to excite by friction a 

 sound similar to that produced by the rumpling of 

 parchment." Now I would remark that as the elytra 

 vibrate in a horizontal plane, the two " files" cannot 

 be rubbed together, because one elytron must neces- 

 sarily pass under the other, and of course both 

 concave surfaces being turned downwards, the two 

 files can never come into contact. This will be 

 evident if we imagine the "files" being placed across 

 the palms of the hands, and one hand passed over the 

 other. None will suppose one of the elytra to be 

 twisted round during the performance. It will be 

 observed that Dr. Brewer describes aright the motions 

 of the " shards," but is in'error, as I think, concerning 

 the production of the sound— or perhaps I should say 

 obscure in the description of the apparatus. We 

 may conceive it possible that the edge of one elytron 

 might by passing under the other rub against the 

 ridge, but the "file" of the other would escape 

 friction by similar means. Besides, the edges are 

 smooth. With regard to the statement in the supple- 

 ment, the assertion that the elytra are raised from 

 the body is correct. Tliis is necessary to allow a 

 greater freedom of motion. 



This elevation also, it will be perceived, suffers them 



to overlap one another to the extent of about one-eighth 

 more of their width, i.e., the entire surface at the lower 

 end, by reason of their bent portion or sides clearing 

 the body, thus removing that check to their free hori- 

 zontal motion. But the simple statement that the sound 

 is caused by friction of the elytra against each other, 

 does not fully explain the matter ; because, as before 

 remarked, but one of the files can be rubbed by its 

 companion elytron ; against what then must the 

 other be rubbed ? It does not seem likely there 

 would be disparity in the actions. Even if the 

 former supposition, namely, that the edge of one 

 elytron rubs against the other, be imagined ; yet it is 

 improbable it could cause much friction, because the 

 edges are curved downwards, so that a blunt rounded 

 edge is presented by each elytron. Thus it could 

 only happen when they were placed vertically that 

 the edge of one could scrape the file of the other. As, 



Fig. i86.— Magnified drawing of elytron of Cricket, showing 

 the " file " placed upon the under surface ; sketched by 

 camera lucida. i. The "file;" 2. Edge formed by the 

 turned-down side ; 3. Inner margin. 



however, I am sure they vibrated in a horizontal 

 plane, it was necessary to seek for some other means 

 whereby friction of both ridges could take place 

 simultaneously, and in a similar manner. The only 

 instruments, from their position capable of accom- 

 plishing this purpose, would appear to be the two 

 lower wings. These have several longitudinal ribs, 

 which, when the wings are folded or shut, present by 

 their approximation a row of ridges over which during 

 the vibration of the elytra the files pass to and fro. 

 They certainly are not very ridged, but are strong and 

 elastic, and must be accepted as playing the part of 

 stationary "bows." I say bows, because evidently 

 the comparatively strong elastic parchment-like 

 elytra must be the sound-boards — "drum" of some 

 persons — of these musical instruments. If a number 

 of fine and closely-placed lines be ruled by means 

 of a diamond upon a piece of copper, and a needle 



