THE SYMPHONY OF VOICES 



set above that of the male, so that she commonly lives in concealment, 

 and is rarely in the company of the male. For her inconspicuous 

 colouring and modest voice are allotted to the female with a view 

 to the task of incubation and the rearing of the young : a task which 

 is essential to the preservation of the species, and which must be 

 performed as inconspicuously as possible, lest the defenceless young 

 should fall easy victims to the enemies of their kind. If the cock 

 assists the female in this task, he is at once provided with protective 

 colouring ; on the other hand, if the young are reared in dark holes 

 or burrows, the female too may wear conspicuous specific markings, 

 and in such cases — as is demonstrated by the parrots — there is no 

 difference in the voices of the two sexes. 



In both sexes the voice, like the coloration, has evolved, in the 

 first place, into a means of recognition. Every bird has its special 

 calls of enticement and warning ; and in the case of birds that live 

 in societies these calls become more various, and develop into an 

 actual language. The same thing is true of such mammals as the 

 monkey, which lead an arboreal life not unlike that of the birds. 

 But even the sound of the footsteps may be pressed into service as 

 a signal of recognition ; and if the experienced hunter can recognize 

 his quarry by its approaching footsteps, it is only natural that the 

 animals themselves should rely on such signs to a much greater 

 extent. In the same way the birds may be recognized by the beat 

 of their wings ; the approaching Humming-bird is announced by the 

 hum of its pinions, and many insects likewise have an audible flight ; 

 and in the Dragonflies the whirring of their glassy wings varies with 

 every species. The Locustidae may be heard at a considerable dis- 

 tance as they fly, especiaUy the gigantic locusts of Brazil ; and there 

 are some which as they fly make a curious clatter with their wings, 

 like the red-and-blue-winged "Clubfoot" of the Alpine meadows. 



In Brazil there are even "Rattle butterflies." Their wings are 

 like black satin, with a pattern of blue spots, and a white stripe 

 runs across each fore-wing. As a general thing they cling to the bark 

 of trees, when their wings (contrary to the usual habit of butterflies) 

 are outspread flat against the tree. If another of the same species 

 approaches, the sitting butterfly flutters away, when one hears a 

 perceptible clatter. Sometimes, too, these butterflies flutter round 

 one another for quite a long time, clattering as they fly. Other 

 Ageroniae have wings that seem covered with white lace. In March 

 these were very common in Pernambuco. They contributed greatly 

 to the beauty of the landscape, and supported the buzzing of the 



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