MR. R. SPRUCE ON INSECT-MIGRATIONS IN SOUTH AMERICA. 365 



lado as the Surubim ; the Murucutu as the Tambaqui ; the Ca- 

 jaru as the Pira-arara, and so on. And if the Tambaqui of the 

 Amazon have been correctly identified with CicTila temensis, then 

 a large fish inhabiting the Temi, a small black-water tributary of 

 the Orinoco, is the same one that abounds in the white water of 

 the Amazon : but this needs confirmation ; for white-water fish are 

 known to shun black waters, and the Tambaqui is (so far as I 

 know) absent from the E-io Negro proper, although it begins to 

 be found a little way within the Casiquiari. 



Supposing these fishes of the Amazon and Orinoco to be really 

 identical, the question arises. Has there been and is there still 

 any migration of fish between those rivers, by way of the Negro 

 and the Casiquiari ? or does their actual distribution date from the 

 period when chains of lakes preceded the rivers to which the 

 waters are now limited, and the colour and properties of the latter 

 were more uniform throughout the whole region ? 



Many of the fishes of the Eio Negro travel up it to spawn, and 

 especially up some of its tributaries ; but the wanderings to and 

 fro of fish in quest of food may be compared to that already noted 

 of wild turkeys ; for the principal subsistence of fish in" the Eiio 

 Negro is on the fruits of riparial trees, some of which seem scarcely 

 touched by either bird or monkey, A small laurel-like bush 

 {Garai'pa laurifolia, S.) lines the banks in many places, and bears 

 damson-like drupes, which are the favourite food of that delicious 

 fish the Uaracu or Aracii. "When the ripe drupes are dropping 

 into the water they attract shoals of Uaracu. Then the fisher- 

 man stations his canoe at dawn of day in the mouth of _some still 

 igarape, overshaded by bushes of Uaracu-Tamacoari -. (the native 

 Indian name of the tree), and with his arrows picks ofi" the fish as 

 they rise to snatch the floating fruits. It ought to be mentioned 

 that the fish of the Negro, if much fewer, are some of them per- 

 haps superior in flavour to any Amazon fish, whereof the TJaracix 

 is an example, and the large Pirahyba is another, the latter being 

 so luscious that it is difficult to know when one has had enough 

 of it, whereas the same or a very closely allied species of the 

 Amazon is often scarcely edible*. 



I have, in what precedes, purposely avoided speaking of the way 

 in which animals prey on each other, because the ultimate mea- 

 sure of the amount of animal life must always depend on that of 



* For further information on the fishes of the Eio Negro I must refer to 

 Mr. Wallace's interesting account of that river (' Travels,' chs. 9, 10 & 16), and 

 to Schomburgk's 'Fishes of Guiana.' 



