HUMBOLDT ON BITING DIPTERA 13 
in the evening the air is filled with mosquitos, which are not, as has been stated 
in some travellers’ stories, of the shape of our European gnats, but of that 
of a little fly. These are the Simuliums. . . . Their bite is as painful as that of 
Stomozys. It leaves a little reddish brown spot which is very excruciating and 
is the extravasated and coagulated blood where the beak has pierced the skin. 
An hour before the sun sets these creatures are replaced by a species of small 
gnat called tempraneros (one which shows itself early) because they appear also 
at sunrise ; their presence lasts one hour and a half; they disappear between six 
and seven o’clock, or, as they say here, after the Angelus. After some minutes 
of sleep one is bitten by the zancudos, another species of gnat with very long 
legs. The zancudos, whose beak forms a piercing sucker, causes the sharpest 
pain and an inflammation which lasts several weeks. Its song is like that of 
our European gnat, but it is stronger and more prolonged. The indians claim 
to recognize the zancudos and the tempraneros by their song; these latter are 
true twilight insects, while the zancudos are nocturnal and disappear towards 
sunrise. 
“In the journey from Carthagena to Santa Fé de Bogota we have observed 
between Mompox and Honda, in the valley of the Rio Grande de la Magdalena, 
zancudos filling the air from eight o’clock in the evening until midnight, dimin- 
ishing about midnight and hiding themselves three or four hours, and return- 
ing in clouds with a devouring appetite about four o’clock in the morning. 
What is the cause of these alternations of movement and repose? Are these 
animals tired by a long flight? On the Orinoco it is very rare to see true day 
gnats, while on the Magdalena one is bitten day and night except for about 
two hours at midday. The zancudos of the two rivers are without doubt of dif- 
ferent species. Are the eyes of one of these species affected by the light of the 
sun more than the eyes of the other species? . . . 
“ At a time when they had not yet studied the geography of animals and 
plants they often confounded the analogous species of different climates. They 
thought that in Japan, in the Andes and at the Strait of Magellan the pines, 
the Ranunculus, the deers, rats, and the Nemocera were the same as those of 
Europe. Celebrated naturalists have thought that the gnat of the torrid zone 
was the same as the gnat of the European marshes, only more vigorous, more 
ferocious, and more dangerous under the influence of a burning climate. This 
opinion is very erroneous. I have examined and described with care upon 
the spot the zancudos with which one is most tormented. On the rivers of 
Magdalena and Guayaquil there are five very distinct species. Latreille, the 
foremost entomologist of the century, has been good enough to revise the detailed 
description of these little animals, which I will give in a note. 
[Here follow the Latin descriptions of the following new species: Culex cyanopen- 
nis, C. lineatus, C. ferox, C. chloropterus, and C. maculatus.] 
“The species of Culex of South America generally have the wings, the 
thorax and the feet bluish and striped, giving a metallic effect from the mingling 
of spots. Here, as in Europe, the males, which are distinguished by their plu- 
mose antenne, are extremely rare, and one is never pierced except by the females. 
The preponderance of this sex explains the immense increase in numbers of in- 
dividuals, each female laying several hundred eggs. In traveling up one of the 
great rivers of America, one notices that the appearance of a new species of 
Culex announces the proximity of a new tributary. To cite an example of this 
curious phenomenon, Culex lineatus, which belongs to the Cafion of Tamalamé- 
que, is noticed in the valley of the Rio Grande de la Magdalena only at a spot 
north of the juncture of the two rivers. It extends up but not down the Rio 
Grande. Itis in the same way that upon a principal vein the appearance of a 
new substance in the vein rock indicates to the miner the neighborhood of a 
secondary vein joining the first. 
