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The Descent of Man

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that from the noise thus produced being in some<br />

way useful, the rough surfaces were gradually<br />

developed into regular stridulating organs.<br />

Some beetles as they move, now produce,<br />

either intentionally or unintentionally, a shuffling<br />

noise, without possessing any proper organs<br />

for the purpose. Mr. Wallace informs me<br />

that the Euchirus longimanus (a Lamellicorn,<br />

with the anterior legs wonderfully elongated in<br />

the male) "makes, whilst moving, a low hissing<br />

sound by the protrusion and contraction <strong>of</strong> the<br />

abdomen; and when seized it produces a grating<br />

sound by rubbing its hind-legs against the<br />

edges <strong>of</strong> the elytra." <strong>The</strong> hissing sound is clearly<br />

due to a narrow rasp running along the sutural<br />

margin <strong>of</strong> each elytron; and I could likewise<br />

make the grating sound by rubbing the shagreened<br />

surface <strong>of</strong> the femur against the granulated<br />

margin <strong>of</strong> the corresponding elytron; but I<br />

could not here detect any proper rasp; nor is it<br />

likely that I could have overlooked it in so large<br />

an insect. After examining Cychrus, and rea-

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