Page:Popular Science Monthly Volume 27.djvu/624

 not resemble that of any of our native birds, being maintained by rapid vibrations of the wings, which enable them to remain apparently motionless in one spot for a considerable time. Their passage from place to place is effected by a series of rapid darts, almost too swift for the eye to follow. Their flight might perhaps be best compared to that of a moth. Like these insects, the humming-birds hover for long over a flower, sipping the honey with their long, thin bill, and in other particulars also—in color and form, for example—humming-birds and moths offer some remarkable parallels. Representatives of each may be found, to distinguish between which needs a close scrutiny, and which, when on the wing, might perplex the best observer. To all outward appearance the humming-birds are birds when at rest, insects when in motion.

The tongue of the humming-bird is admirably adapted for extracting the honey from flowers, being really a suctorial tongue in the truest sense of the expression. Long and tubular, often bifid and hairy at the tip, this organ serves to catch the insects that may be concealed in the flower (Fig. 22, I). The beak is long, thin, and pointed; the upper

jaw closes over the edges of the lower jaw, thus forming a kind of tube incasing the tongue. In almost all species the beak is straight or very slightly curved (Figs. 20-22); in the sickle-beak alone (the Eutoxeres aquila of the equator, for example) it is sickle-shaped. The length of the beak varies in accordance with the length of the corolla-tube of the flowers habitually visited by the different species. In the Heliactinus cornutus of Brazil (Fig. 21) it is 1*5 centimetre long, in the Heliothrix aurita of Minas-Geraës in Brazil (Fig. 20) about two centimetres. The longest beak among the humming-birds is that of the