In Patagonia, where the phenomenon of dragon-fly storms
is also known, an Englishman residing at the Rio Negro
related to me the following occurrence which he witnessed
there. A race meeting was being held near the
town of El Carmen, on a high exposed piece of ground,
when, shortly before sunset, a violent pampero wind
came up, laden with dense dust-clouds. A few
moments before the storm broke, the air all at once
became obscured with a prodigious cloud of dragon-flies.
About a hundred men, most of them on horseback, were
congregated on the course at the time, and the insects,
instead of rushing by in their usual way, settled
on the people in such quantities that men and horses
were quickly covered with clinging masses of them.
My informant said—and this agrees with
my own observation—that he was greatly impressed
by the appearance of terror shown by the insects;
they clung to him as if for dear life, so that he
had the greatest difficulty in ridding himself of them.
Weissenborn, in London’s Magazine of Natural
History (N. S. vol. iii.) describes a great
migration of dragon-flies which he witnessed in Germany
in 1839, and also mentions a similar phenomenon occurring
in 1816, and extending over a large portion of Europe.
But in these cases the movement took place at the
end of May, and the insects travelled due south; their
migrations were therefore similar to those of birds
and butterflies, and were probably due to the same
cause. I have been unable to find any mention
of a phenomenon resembling the one with which we are
so familiar on the pampas, and which, strangely enough,
has not been recorded by any European naturalists
who have travelled there.
CHAPTER X.
MOSQUITOES AND PARASITE PROBLEMS.
There cannot be a doubt that some animals possess
an instinctive knowledge of their enemies—or,
at all events, of some of their enemies—though
I do not believe that this faculty is so common as
many naturalists imagine. The most striking example
I am acquainted with is seen in gnats or mosquitoes,
and in the minute South American sandflies (Simulia),
when a dragon-fly appears in a place where they are
holding their aerial pastimes. The sudden appearance
of a ghost among human revellers could not produce
a greater panic. I have spoken in the last chapter
of periodical storms or waves of dragon-flies in the
Plata region, and mentioned incidentally that the
appearance of these insects is most welcome in oppressively
hot weather, since they are known to come just in
advance of a rush of cool wind. In La Plata we
also look for the dragon-fly, and rejoice at its coming,
for another reason. We know that the presence
of this noble insect will cause the clouds of stinging
gnats and flies, which make life a burden, to vanish
like smoke.
Copyrights
The Naturalist in La Plata from Project Gutenberg. Public domain.
