HUMMING-BIRDS 



of being excessively long and pointed; their plumage is 

 arranged differently; and their feet are long and strong, 

 instead of being excessively short and weak. There remain 

 only the superficial characters of small size and brilliant 

 metallic colours to assimilate them with the humming-birds, 

 and one structural feature a tubular and somewhat extensile 

 tongue. This, however, is a strictly adaptive character, the 

 sun-birds feeding on small insects and the nectar of flowers, 

 just as do the humming-birds ; and it is a remarkable instance 

 of a highly peculiar modification of an organ occurring inde- 

 pendently in two widely-separated groups. In the sun-birds 

 the hyoid or tongue-muscles do not extend so completely over 

 the head as they do in the humming-birds, so that the tongue 

 is less extensible ; but it is constructed in exactly the same 

 way by the inrolling of the two laminae of which it is 

 composed. 



The tubular tongue of the sun-birds is a special adaptive 

 modification acquired within the family itself, and not 

 inherited from a remote ancestral form. This is shown by 

 the amount of variation this organ exhibits in different mem- 

 bers of the family. It is most highly developed in the 

 Arachnotheras, or spider-hunters of Asia, which are sun-birds 

 without any metallic or other brilliant colouring. These 

 have the longest bills and tongues, and the most developed 

 hyoid muscles ; they hunt much about the blossoms of palm- 

 trees, and may frequently be seen probing the flowers while 

 fluttering clumsily in the air, just as if they had seen and 

 attempted to imitate the aerial gambols of the American 

 humming-birds. The true metallic sun-birds generally cling 

 about the flowers with their strong feet; and they feed 

 chiefly on minute hard insects, as do many humming-birds. 

 There is, however, one species (Chalcoparia phoenicotis), 

 always classed as a sun-bird, which differs entirely from the 

 rest of the species in having the tongue flat, horny, and forked 

 at the tip ; and its food seems to differ correspondingly, for 

 small caterpillars were found in its stomach. More remotely 

 allied, but yet belonging to the same family, are the little 

 flower-peckers of the genus Diceum, which have a short bill 

 and a tongue twice split at the end ; and these feed on small 

 fruits, and perhaps on buds and on the pollen of flowers. The 



