THE MOSAIC OF COLOURS 



Other insects; and in particular for the Flies, which do not make 

 much use of protective colouring. — Brazil, by the way, boasts of the 

 largest flies in the world; great flies with bodies as long and thick 

 as one's little finger, which resemble the great hornets of which 

 I shall presently speak (Plate 29, II, 15). — The Beetles, however, 

 offer a rich harvest for those who wish to study protective coloration. 

 There are all sorts of green beetles, and others coloured like the 

 bark of trees, and some whose bodies have even the rough and 

 irregular surface of bark. The Weevils especially are past-masters 

 in such adaptations. Among them are forms like the Brenthidae 

 (Plate 29, II, 5), so long and thin that the insect resembles a twig. 

 The Capricorns too contain many species which in form and colour 

 show the most successful adaptation to their environment. 



When night falls over the landscape protective coloration and 

 characteristic markings are lost in the general obscurity; only the 

 white of nocturnal flowers interrupts the shadows, while the bats 

 and nightjars betray their identity by the manner of their flight 

 as they shine against the lighter sky. 



But suddenly signals blaze and blink which can be perceived 

 further than the brightest colours in the daytime. The fireflies have 

 begun their play : the fitting and visible expression of the bewildering 

 magic of the tropical night. Before ever I came to Brazil I had 

 seen in Ceylon the scattering sparks of the fireflies above the dark 

 meadows, and the thousands of green lights glittering in the trees, 

 which were thus transformed into very Christmas-trees; an unfor- 

 gettable spectacle. In Brazil I was once more to enjoy the play of 

 the green lights. In Petropolis, on New Year's Eve, as I walked 

 through the gardens in the fragrant summer night, the lawns were 

 as though illuminated, and with astonishment I noted how hundreds 

 of green lights blazed out simultaneously, and were simultaneously 

 extinguished; with so regular a rhythm that it seemed as though 

 the sparks were blown upon by a huge mechanical bellows that 

 gave a puff" every second. Of this extraordinary rhythm I could 

 discover no explanation. 



The species of firefly or luminous beetle which I have just de- 

 scribed has, like its European relatives, a luminous organ on the 

 underside of the last two segments of the abdomen. The light is 

 produced by a substance which is decomposed, or rather oxydized, 

 by the oxygen in the spiracles surrounding the organ, under the 



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