MB. R. SPRUCE ON IKSECT-MIGRATIONS IN SOUTH AMERICA. 347 



geological constitution, and even of the climate — to which the 

 range of the larger Mammals and Birds corresponds in a consider- 

 able degree, but not that of any one class or tribe of animals, and 

 especially not of lepidopterous Insects. These features depend on 

 the prevalence of certain groups, or even of single species, of 

 plants over vast areas : — one set prevailing in the Virgin or Grreat 

 Forests {Gaa-guaqu of the Brazilians, Monte Alto of the Venezue- 

 lans) which clothe the fertile lands beyond the reach of inunda- . 

 tions, and constitute the great mass of the vegetation ; another in 

 the Low or White Forests {Caa-tinga, Monte Bajo) — those curious 

 remnants of a still more ancient and humbler but surpassingly 

 interesting vegetation, which (especially on the Eio Negro and 

 Casiquiari) are being gradually hemmed in and supplanted by the 

 sturdier growth of the Great Forests, wherein they are interspersed 

 like flower-beds in a shrubbery ; another in the Riparial Forests 

 {Ygapu or Gap 0, Rebalsd), on lowlands bordering the rivers, and 

 laid under water for several months in the year, where the trees 

 when young, and the bushes throughout their existence, must 

 have the curious property of being able to survive complete and 

 prolonged submersion, constituting for them a species of hyber- 

 nation; a fourth in the Eecent Forests {Caa-puera, Basti'ojo), 

 which spring up to replace the Primitive Forests destroyed by 

 man, and, notwithstanding their weedy character, consist chiefly 

 of shrubs and trees ; a fifth in the Savannas or Campos — grassy 

 or scrubby knolls, or glades, or hollows (dried-up lakes), which 

 bear a very small proportion indeed to the vast extent of wood- 

 land, in the Amazon A'-alley proper, but towards its northern and 

 southern borders compete with the woods for the possession of the 

 ground, and in the centre of Venezuela enlarge to interminable 

 grassy " llanos " or plains. 



From an elevated site that should embrace the landscape on all 

 sides to the extreme limit of vision, as, for instance, from the 

 heights at the confluence of the Eio Negro and Amazon, or, better 

 still, from one of the steep granite rocks that overlook the noble 

 forests of the Casiquiari, a practised eye would distinguish the 

 various kinds of forest by their aspect alone. The Virgin Forests 

 are distinct enough by the sombre foliage of the densely-packed, 

 lofty trees, out of which stand, like the cupolas, spires, and turrets 

 of a large city, the dome-shaped or pyramidal or flat-topped crowns 

 of still loftier trees, overtopping even the tallest palms, both 

 palms and trees being more or less interwoven with stout gaily- 

 flowering lianas ; the White Forests by the low neat-grov»-ing and 



