Ch. 15: The Death-feigning Instinct

Most people are familiar with the phenomenon of "death-feigning,"
commonly seen in coleopterous insects, and in many spiders. This highly
curious instinct is also possessed by some vertebrates. In insects it is
probably due to temporary paralysis occasioned by sudden concussion, for
when beetles alight abruptly, though voluntarily, they assume that
appearance of death, which lasts for a few moments. Some species,
indeed, are so highly sensitive that the slightest touch, or even a
sudden menace, will instantly throw them into this motionless,
death-simulating condition. Curiously enough, the same causes which
produce this trance in slow-moving species, like those of Scarabseus for
example, have a precisely contrary effect on species endowed with great
activity. 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. Though they could see it, it was impossible to throw the
lasso over its head, and, after vainly trying to dislodge it, they at
length set fire to the reeds. Still it refused to stir, but lay with
head erect, fiercely glaring at them through the flames. Finally it
disappeared from sight in the black smoke; and when the fire had burnt
itself out, it was found, dead and charred, in the same spot.

On the pampas the gauchos frequently take the black-necked swan by
frightening it. When the birds are feeding or resting