that the males stridulate in order to call or to excite the females;
but with most beetles the stridulation apparently serves both sexes as
a mutual call. Beetles stridulate under various emotions, in the same
manner as birds use their voices for many purposes besides singing to
their mates. The great Chiasognathus stridulates in anger or defiance;
many species do the same from distress or fear, if held so that they
cannot escape; by striking the hollow stems of trees in the Canary
Islands, Messrs. Wollaston and Crotch were able to discover the
presence of beetles belonging to the genus Acalles by their
stridulation. Lastly, the male Ateuchus stridulates to encourage the
female in her work, and from distress when she is removed. (79. M. P.
de la Brulerie, as quoted in Journal of Travel, A. Murray, vol. i.
1868, p. 135.) Some naturalists believe that beetles make this noise to
frighten away their enemies; but I cannot think that a quadruped or
bird, able to devour a large beetle, would be frightened by so slight a
sound. The belief that the stridulation serves as a sexual call is
supported by the fact that death-ticks (Anobium tessellatum) are well
known to answer each other s ticking, and, as I have myself observed, a
tapping noise artificially made. Mr. Doubleday also informs me that he
has sometimes observed a female ticking (80. According to Mr.
Doubleday, the noise is produced by the insect raising itself on its
legs as high as it can, and then striking its thorax five or six times,
in rapid succession, against the substance upon which it is sitting.
For references on this subject see Landois, Zeitschrift fur wissen.
Zoolog. B. xvii. s. 131. Olivier says (as quoted by Kirby and Spence,
Introduction to Entomology, vol. ii. p. 395) that the female of
Pimelia striata produces a rather loud sound by striking her abdomen
against any hard substance, and that the male, obedient to this call,
soon attends her, and they pair. ), and in an hour or two afterwards
has found her united with a male, and on one occasion surrounded by
several males. Finally, it is probable that the two sexes of many kinds
of beetles were at first enabled to find each other by the slight
shuffling noise produced by the rubbing together of the adjoining hard
parts of their bodies; and that as those males or females which made
the greatest noise succeeded best in finding partners, rugosities on
various parts of their bodies were gradually developed by means of
sexual selection into true stridulating organs.
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