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The Descent of Man

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coloured; and as these insects emit an extremely<br />

nauseous odour, their conspicuous colours<br />

may serve as a signal that they are unpalatable<br />

to insectivorous animals. In some few cases<br />

their colours appear to be directly protective:<br />

thus Pr<strong>of</strong>. H<strong>of</strong>fmann informs me that he could<br />

hardly distinguish a small pink and green species<br />

from the buds on the trunks <strong>of</strong> lime-trees,<br />

which this insect frequents.<br />

Some species <strong>of</strong> Reduvidae make a stridulating<br />

noise; and, in the case <strong>of</strong> Pirates stridulus, this<br />

is said (22. Westwood, 'Modern Classification<br />

<strong>of</strong> Insects,' vol. ii. p. 473.) to be effected by the<br />

movement <strong>of</strong> the neck within the pro-thoracic<br />

cavity. According to Westring, Reduvius personatus<br />

also stridulates. But I have no reason to<br />

suppose that this is a sexual character, excepting<br />

that with non-social insects there seems to<br />

be no use for sound-producing organs, unless it<br />

be as a sexual call.

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