IV 
HUMMING-BIRDS 
335 
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 laminse 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 
Arachnotherse, 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 
