CiiAr. VII. DESCENT TO PARA. 347 



tlie species, although extremely numerous (about 300 

 are known in collections), are nearly all very rare. It 

 is worthy of note that mimicking insects are very 

 generally of great scarcity ; that is, few examples of each 

 species occur in the places where they are found, and 

 they constitute groups which are remarkable for the 

 strongly-marked diversity and limited ranges of their 

 species. 



After we had rested some weeks in Barra,we arranged 

 our plans for further explorations in the interior of the 

 country. Mr. Wallace chose the Rio Negro for his 

 next trip, and I agreed to take the Solimoens. My 

 colleague has already given to the world an account of 

 his journey on the Rio Negro, and his adventurous 

 ascent of its great tributary the Uapes. I left Barra for 

 Ega, the first town of any importance on the Soli- 

 moens, on the 26th of March, 1850. The distance is 

 nearly 400 miles, which we accomplished in a small 

 cuberta, . manned by ten stout Cucama Indians, in 

 thirty-five days. On this occasion, I spent twelve 

 months in the upper region of the Amazons ; circum- 

 stances then compelled me to return to Para. I 

 revisited the same country in 1855, and devoted three 

 years and a-half to a fuller exploration of its natural 

 productions. The results of both journies will be 

 given together in subsequent chapters of this work ; in 

 the meantime, I will proceed to give an account of 

 Santarem and the river Tapajos, whose neighbourhoods 

 I investigated in the years 1851-4. 



A few words on my visit to Para in 1851, may be 



