Rapacious beetles, when disturbed, scuttle quickly out of
sight, and some water-beetles spin about the surface, in circles or
zigzag lines, so rapidly as to confuse the eye. Our common long-legged
spiders (Pholcus) when approached draw their feet together in the middle
of the web, and spin the body round with such velocity as to resemble a
whirligig.
Certain mammals and birds also possess the death-simulating instinct,
though it is hardly possible to believe that the action springs from the
same immediate cause in vertebrates and in insects. In the latter it
appears to be a purely physical instinct, the direct result of an
extraneous cause, and resembling the motions of a plant. In mammals and
birds it is evident that violent emotion, and not the rough handling
experienced, is the final cause of the swoon.
Passing over venomous snakes, skunks, and a few other species in which
the presence of danger excites only anger, fear has a powerful, and in
some cases a disabling, effect on animals; and it is this paralyzing
effect of fear on which the death-feigning instinct, found only in a few
widely-separated species, has probably been built up by the slow
cumulative process of natural selection.
I have met with some curious instances of the paralyzing effect of fear.
I was told by some hunters in an outlying district of the pampas of its
effect on a jaguar they started, and which took refuge in a dense clump
of dry reeds.
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