PERIODS OF APPEARANCE AND DISAPPEARANCE. . 277 
a species of small gnats, called tempraneros* because they 
appear also at sunrise, take the place of the mosquitos. 
Their presence scarcely lasts an hour and a half ; they dis- 
appear between sis and seven in the evening, or, as they 
say here, after the Angelus (a la oracion). After a few mi- 
nutes’ repose, you feel yourself stung by zancudos, another 
species of gnat with very long legs. The zancudo, the pro- 
boscis of which contains a sharp-pointed sucker, causes the 
niost acute pain, and a swelling that remains several weeks. 
Its hum resembles that of the European gnat, but is louder 
a nd more prolonged. The Indians pretend to distinguish 
the zancudos and the tempraneros “by their song;” the 
tatter are real twilight insects, while the zancudos are most 
frequently nocturnal insects, and disappear toward sunrise. 
In our way from Carthagena to Santa Ee de Bogota, we 
observed that between Mompox and Honda, in the valley of 
the Rio Magdalena, the zancudos darkened the air from 
®ight in the evening till midnight; that towards midnight 
they diminished in number, and were hidden for three or 
tour hours ; and lastly that they returned in crowds, about 
four in the morning. "What is the cause of these alternations 
motion and rest ? Are these animals fatigued by long 
tight ? It is rare on the Orinoco to see real gnats by day ; 
^hile at the Rio Magdalena we were stung night and day, 
oxeept from noon till about two o’clock. The zancudos of 
the two rivers are no doubt of different species. 
, "We have seen that the insects of the tropics everywhere 
follow a certain standard in the periods at which they alter- 
?ately arrive and disappear. At fixed and invariable hours, 
^ the same season, and the same latitude, the air is peopled 
new inhabitants, and in a zone where the barometer 
ocomes a clock,* where everything proceeds with such ad- 
orable regularity, we might guess blindfold the hour of the 
or night, by the hum of the insects, and by their stings, 
,, ‘Which appear at an early hour’ ( temprano ). Some persons say, 
the zancudo is the same as the tempranero, which returns at night, 
er . hiding itself for som etime. I have doubts of this identity of the 
j?i cies ! the pain caused by the sting of the two insects appeared to me 
Querent. 
I 'W the extreme regularity of the horary variations of the atmospheric 
