Dragon-Fly Storms. 131 
that they appear only when flying before the south- 
west wind, called pampero—the wind that blows 
from the interior of the pampas. The pampero 
is a dry, cold wind, exceedingly violent. It bursts 
on the plains very suddenly, and usually lasts only 
a short time, sometimes not more than ten minutes; 
it comes irregularly, and at all seasons of the year, 
but is most frequent in the hot season, and after 
exceptionally sultry weather. It is in summer and 
autumn that the large dragon-flies appear ; not with 
the wind, but—and this is the most curious part of 
the matter—in advance of it; and inasmuch as 
these insects are not seen in the country at other 
times, and frequently appear in seasons of pro- 
longed drought, when all the marshes and water- 
courses for many hundreds of miles are dry, they 
must of course traverse immense distances, flying 
before the wind at a speed of seventy or eighty miles 
an hour. On some occasions they appear almost 
simultaneously with the wind, going by like a flash, 
and instantly disappearing from sight. You have 
scarcely time to see them before the wind strikes 
you. As arule, however, they make their appear- 
ance from five to fifteen minutes before the wind 
strikes; and when they are in great numbers the 
air, to a height of ten or twelve feet above the 
surface of the ground, is all at once seen to be full 
of them, rushing past with extraordinary velocity 
im a north-easterly direction. In very oppressive 
weather, and when the swiftly advancing pampero 
brings no moving mountains of mingled cloud and 
dust, and is consequently not expected, the sudden 
apparition of the dragon-fly is a most welcome one, 
