Chap. YII. PIUM FLTES. 333 



vicinity were clothed with ferns, large-leaved species 

 belonging to the genus Lygodium, which, like Osmunda, 

 have their spore-cases collected together on contracted 

 leaves. On the 18th, we arrived at a large fazenda 

 (plantation and cattle-farm), called Jatuarana. A rocky 

 point here projects into the stream, and as we found it 

 impossible to stem the strong current which whirled 

 round it, we crossed over to the southern shore. Canoes, 

 in approaching the Rio Negro, generally prefer the 

 southern side on account of the slackness of the current 

 near the banks. Our progress, however, was most tedi- 

 ously slow, for the regular east wind had now entirely 

 ceased, and the vento de cima or wind from up river, 

 having taken its place, blew daily for a few hours, dead 

 against us. The weather was oppressively close, and 

 every afternoon a squall arose, which, however, as it 

 came from the right quarter and blew for an hour or 

 two, was very welcome. We made acquaintance on this 

 coast with a neAv insect pest, the Pium, a minute fly, 

 two-thirds of a line in length, which here commences its 

 reig^n, and continues henceforward as a terrible scourp'e 

 along the upper river, or Solimoens, to the end of the 

 navigation on the Amazons. It comes forth only by 

 day, relieving the mosquito at sunrise with the greatest 

 punctuality, and occurs only near the muddy shores 

 of the stream, not one ever being found in the shade 

 of the forest. In places where it is abundant it accom- 

 panies canoes in such dense swarms as to resemble 

 thin clouds of smoke. It made its appearance in this 

 way the first day after we crossed the river. Before I 

 was aware of the presence of flies, I felt a sHght itching 



