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place, and no pain is left behind. We often re- 

 peated this experiment on ourselves in the valley 

 of the Rio Magdalena, by the advice of the 

 natives. It may be asked, whether the insect 

 deposit the stimulating liquid only at the 

 moment of it's flight, when it is driven away, or 

 repump the liquid, when it is left to suck as 

 much as it will. I incline to this latter opinion ; 

 for on presenting quietly the back of the hand to 

 the culex cyanopterus, I observed, that the pain, 

 very violent in the beginning, diminishes in pro- 

 portion as the insect continues to suck ; and 

 ceases altogether, when it voluntarily flies away. 

 I also tried to wound my skin with a pin, and 

 rubbed the pricks with bruised moschettoes 

 (mosquitos machucados) ; and no swelling ensued. 

 The irritating liquor of the dipterae nemocerae, 

 in which the chemists have not yet recognized 

 any acid properties, is contained as in the ant, 

 and other hymenopterous insects, in particular 

 glands ; and is probably too much diluted, and 

 consequently too much weakened, if the skin be 

 rubbed with the whole of the bruised insect. 



I have united at the close of this chapter all 

 we learned during the course of our travels on 

 phenomena, which naturalists have singularly 

 neglected hitherto, though they exert a great 

 influence on the welfare of the inhabitants, the 

 salubrity of the climate, and the establishment 

 of new colonies on the rivers of equinoctial 



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