to an Insect Fauna of the Amazon Valley. 225 



nificent river, here three to four miles broad, form, what the 

 botanical traveller Pceppig, who describes with so much feeling 

 the scenery of the Andes in crossing the continent, *' eine un- 

 beschreiblich herrliche Landschaft." Westward they terminate 

 on the north at the mouth of the Trombetas, although the elevated 

 land extends as far as the Rio Negro. On the south the hills are 

 conspicuous only along the coast, extending about 100 miles below 

 Santarem ; westward the high undulating country continues at 

 some distance from the river, past Villa Nova to the banks of 

 the Madeira. The whole of this district, however, is not quite 

 uniform in its physical features. In the low lands and the islands 

 in mid-river, especially at the mouths of the rivers, the soil and the 

 forests are very similar to those of the other two regions ; but the 

 general character of the country is such as I have described, and 

 its zoological characters equally peculiar. The Upper Amazons 

 and Para, as we have seen, have more resemblance with each 

 other, in their physical features, than either have with the Lower 

 Amazons. Both have extremely humid climates and a uniform 

 low land. The amount of rain which falls in either is probably 

 nearly alike, but the seasons are rather differently apportioned ; 

 a circumstance which must affect in some degree animal life. The 

 Para region, too, is within the influence of the tides ; daily the low 

 lands are twice saturated with humidity. The Upper Amazon, on 

 the contrary, has only the periodical rise and fall of the river ; 

 six months' ebb and six months' flow. During the one season 

 the soil is left free from humidity, and during the other thoroughly 

 saturated with it. Par^ is affected by the daily sea breeze, 

 whilst the Upper Amazon has a generally stagnant, sultry air, or 

 winds of inconstant direction and short duration. The soil, too, 

 is generally much lighter and more sandy in the Para district than 

 on the Upper Amazon, where it is wholly composed of clay and 

 humus. The breadth of the alluvial plain of the Upper Amazon 

 must be far greater than that of any other part of this great river 

 valley ; and throughout the whole region there is the same uni- 

 formity of soil and climate. Its insect fauna is very rich, con- 

 taining many species peculiar to itself. The individuals of the 

 species common to it and the Lower Amazon or Para are generally 

 larger and more brilliantly coloured, or are subject to remarkable 

 variations, whilst very constant in the other districts. Another 

 feature of its fauna is the resemblance to that of the Andean valleys 

 of Bogota and Bolivia, a resemblance which increases with every 

 100 miles in ascending the river. It is well known that the rich- 

 ness of colour, variety of form and number of species of Diurnal 

 Lepidoptera, already so great along the Atlantic coasts of South 



