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 

 alwaj's accompanies irruptive maladies. Whites bom 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 difiiculty 

 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 Maypures, at Atures, 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. . . . 



" I 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 Eio 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 

 vrings {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 Carthagena 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 cafafi 

 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 Simuhum 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 Eio de la Magdalena Culex cyanopterus is the one feared 



• " Perhaps a Culicid." [This is very probably a Culicoides, H., D. & K.] 



