MOSQUITO LOCALITIES 15 
for several weeks, and which increases the irritability of the skin, and which 
throws persons with delicate complexion into that feverish condition which 
always accompanies irruptive maladies. Whites born in equinoctial America, 
and Europeans who have lived a long time in the missions on the borders of the 
forests and of the great rivers, suffer much more than indians, but infinitely less 
than Europeans recently landed. It is not, then, as some travelers say, the thick- 
ness of the skin which renders the bite more or less painful at the moment it is 
experienced ; it is not on account of the particular character of the skin that the 
swellings and the inflammatory symptoms are less with the indians; it is upon 
the nervous irritability of the dermal system that the degree and the duration of 
the trouble depends. This irritability is increased by very warm clothes, by 
the use of alcoholic liquors, and by the habit of scratching the wound; finally, 
and this physiological observation is the result of my own experience, by baths 
taken at too short intervals. In places where the absence of crocodiles allows 
one to enter the river we have observed that the immoderate use of baths, while 
allaying the pain of old zancudo bites, rendered us much more sensitive to new 
bites. If one bathes more than twice a day one gets his skin into a state of 
nervous irritability of which no one in Europe can form any idea. One would 
say that all of his sensitiveness was in his skin. 
“ As the gnats pass two-thirds of their life in the water, it is not surprising 
that in forests traversed by great rivers these injurious insects become more rare 
in proportion as one leaves the river. They seem to prefer to remain near places 
where they have bred and where they are to lay their eggs. As a matter of fact 
the savage indians become accustomed to mission life with greater difficulty 
since in the Christian villages they find a torment which they did not know in 
their own homes in the interior. We have seen at Maypurés, at Aturés, and at 
Esmeralda that the indians fled to the forests solely from fear of mosquitoes. 
Unfortunately all the missions of the Orinoco, from their very beginning, 
have been too near the banks of the river. At Esmeralda the inhabitants assured 
us that if the village had been placed in one of the beautiful plains which sur- 
round the high mountains of Duida and of Maraguaca, they would have breathed 
freely and would have enjoyed some sleep. The ‘great cloud of mosquitos’ 
(this is the expression of the friars) is found only upon the Orinoco and its 
tributaries. This cloud grows less in proportion as one leaves the rivers. . . . 
“T have learned that these little insects make migrations from time to time, 
like the monkeys that live gregariously. At the beginning of the rainy season 
certain species, by which we have not yet been bitten, are found in certain 
places. We have been informed that on the Rio de la Magdalena, at Simiti, they 
know no other Culex than the jejen. One can pass the night there peacefully, 
for the jejen is not a nocturnal insect. Since 1801 the large gnat with blue 
wings (Culex cyanopterus) has become so abundant that the poor inhabitants of 
Simiti do not know how to obtain a peaceable nap. On the swampy canals of 
the island of Baru, near Carthagéna des Indes, there is a little whitish fly known 
as the cafafi.* It is scarcely visible to the naked eye, and causes very painful 
swellings. It is necessary to wet the mosquito bars in order to prevent the cafaft 
from working through them. This insect, fortunately rare elsewhere, comes up 
in January by the canal to Morales. When we were in this village in the month 
of May we found Simulwum and zancudos, but more of the jejen. 
“ Slight changes in nourishment and in climate appear to change the activity 
of the poison in the same species of gnats or mosquitoes. On the Orinoco the 
most voracious insects are those of the Grand Cataracts, of Esmeralda and of 
Mandavaca. On the Rio de la Magdalena Culex cyanopterus is the one feared 
*“ Perhaps a Culicid.” [This is very probably a Culicoides, H., D. & K.] 
