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THE POPULAR SCIENCE MONTHLY. 



Fig. 3. Cicada. 



to represent the rushing of the swarms of locusts which afflicted 

 the Nile country as the seventh plague, by a principal viola. 



Several other species of in- 

 sects have apparatus for pro- 

 ducing sounds similar to that 

 of the grasshopper, or modifica- 

 tions of it. Of a different type 

 is that with which the cicadas 

 (Fig. 3) are endowed the only 

 creatures of this class which 

 have vocal apparatus analogous 

 to those of the higher animals. 

 Only the males of this family are singers, for which the Greek 

 poets called them happy because their females were dumb. With 

 the ancients, a cicada sitting on a harp was the symbol of music. 

 A pretty fable tells of the contest between two cithara-players, 

 in which the curious event happened that when one of the con- 

 testants broke a string, a singing cicada sprang on his harp and 

 helped him out so that he gained the prize. The Greeks, who 

 shut the insects in cages so as to be sung to by them in their sleep, 

 were at odds concerning the nature of their singing apparatus ; 

 and the controversy among naturalists on the subject lasted till 

 very recently. The zoologist H. Landois, who 

 investigated the difficult subject of animal 

 sounds with ceaseless industry and great skill, 

 was able to give a satisfactory solution to the 

 question. According to his research, the case is 

 one in which the sound is really made by air 

 circulating through passages in the interior of 

 the body. Every insect's body is penetrated by 

 a system of breathing-tubes or tracheae which 

 open at places on the surface. The openings 

 are called stigmata. This system of breathing- 

 tubes, through which the air is inspired and 

 expired, takes the place of the lung of the higher 

 animals. Landois discovered them in very ob- 

 scure parts of the cicada, and found that they 

 form a kind of windpipe representing the actual 

 tone-factory of the animals. This air cavity is, ( 4. Tone Ai>pa- 

 as the picture (Fig. 4) shows, not quite open, but eatus of the Cicada 

 has only a narrow cleft {sp), through which the 

 air goes in and out. The cleft is formed by two 

 stretched membranes (sa and sb), which vibrate when the air passes 

 through. They serve, in fact, a like function with the vocal cords 

 of our larynx. They lie, besides, opposite a large cavity over which 

 a folded membrane is stretched like a drum-head upon a hard 



( magnified 

 times). 



thirty 



