430 LAND ANIMALS 



At first sight, the tropical rain-forest, with its luxuriance of plant 

 life, appears discouragingly poor in animals. This is in part due to 

 the fact that the animals readily hide behind the tangle of vines, 

 trunks, roots, and branches and may live unnoticed in the high forest 

 canopy. Frequently, if adequate trails are lacking, one must rely on 

 hearing rather than sight for evidence of the presence of animal life. 

 Many of the mammals, including some monkeys, move about the forest 

 mainly after sunset. During the day, silence may reign, a stillness 

 which some travelers describe as oppressive although the monotony 

 is broken now and then by the cry of a bird, or the passing of a noisy 

 flock, the humming of a swarm of bees, or the calls of a group of 

 chattering or howling monkeys. 



In or near the clearings produced naturally by the crashing of a 

 giant tree, by streams, or at the natural forest margins, where uni- 

 formity ceases, where air movement is increased, where light pene- 

 trates and temperatures fluctuate, life becomes astonishingly abundant. 

 No place offers a richer insect life than does a recently cut forest 

 clearing. Here the butterflies may appear in clouds; metallic golden 

 buprestid beetles, magnificent cerambycid beetles, gay hemipterans, 

 and hymenopterous insects are abundant. A collector may take more 

 species in a month in such a locality than in a year in the depths of 

 an undisturbed forest. 31 



It is in such places that the traveler experiences the many-voiced, 

 ear-deafening nocturnal concerts of the tropical rain-forest. With the 

 sudden approach of darkness, as if by command, cicadas and crickets 

 burst into sharp metallic song; various tree frogs join; 32 flocks of 

 parrots and parakeets settle noisily into their nesting places; and in 

 America, the voices of the howling monkeys add to the uproar. In 

 places this evening music increases at sundown to become an in- 

 harmonious roar of life such as Humboldt described on the upper 

 Orinoco. 33 Later the larger animals become quiet and only the concert 

 of the insects and the tree frogs continues during the night. With the 

 approach of dawn comes another period of noise. The harsh voices of 

 birds of the tropical forests appear to be developed as group or species 

 signals replacing visual stimuli as a method of group integration. 



Within the forests, the invertebrates are generally well hidden. 

 AVorms, snails, millipeds, centipeds, scorpions, isopods, spiders, and 

 insect larvae retire under loose bark or decaying logs or into the 

 axillae of palms. Land planarians crawl into the ground during the 

 day and peripatus lives during the drier periods well buried below 

 decaying logs or stumps. 



Land leeches not only live on the ground but also climb bushes, 



