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 on the grass, two
or three men or boys on horseback go quietly to leeward of the flock,
and when opposite to it suddenly wheel and charge it at full speed,
uttering loud shouts, by which the birds are thrown into such terror
that they are incapable of flying, and are quickly despatched.