200 The Naturalist in La Plata. 
is, for purposes of bird-portraiture, as good as a live 
robin ; the same may be said of even many brilliant- 
plumaged species less aérial in their habits than 
humming-birds. In butterflies the whole beauty is 
seldom seen until the insect is dead, or, at any rate, 
captive. It was not when Wallace saw the 
Ornithoptera croesus flying about, but only when 
he held it in his hands, and opened its glorious 
wings, that the sight of its beauty overcame him so 
powerfully. The special kind of beauty which 
makes the first sight of a humming-bird a revelation 
depends on the swift singular motions as much as 
on the intense gem-like and metallic brilliancy of 
the plumage. 
The ininute exquisite form, when the bird hovers 
on misty wings, probing the flowers with its coral 
spear, the fan-hke tail expanded, and poising 
motionless, exhibits the feathers shot with many 
hues; and the next moment vanishes, or all but 
vanishes, then reappears at another flower only to 
vanish again, and so on successively, showing its 
splendours not continuously, but like the intermitted 
flashes of the firefly—this forms a picture of airy 
grace and loveliness that baffles description. All 
this glory disappears when the bird is dead, and 
even when it alights to rest ona bough. Sitting 
still, it looks like an exceedingly attenuated king- 
fisher, without the pretty plumage of that bird, but 
retaining its stiff artificial manner. No artist has 
been so bold as to attempt to depict the bird as it 
actually appears, when balanced before a flower the 
swift motion of the wings obliterates their form, 
making them seem lke a mist encircling the body : 
