They feed exclusively on these insects, and are never seen where the locusts are not.

They follow them through all their migrations, building their nests, and rearing their young, in the midst of their prey! It was, indeed, a curious sight to look upon, that swarm of winged insects, and their numerous and varied enemies; and all stood gazing upon it with feelings of wonder.

Still the living cloud approached no nearer, and the hopes of Von Bloom continued to rise.
The swarm kept extending to the south--in fact, it now stretched along the whole western horizon; and all noticed that it was gradually getting lower down--that is, its top edge was sinking in the heavens.

Were the locusts passing off to the west?
No.
"Da am goin' roost for da nacht--now we'll get 'em in bagfull," said Swartboy, with a pleased look; for Swartboy was a regular locust-eater, as fond of them as either eagle or kite,--ay, as the "springhaan-vogel" itself.
It was as Swartboy had stated.

The swarm was actually settling down on the plain.
"Can't fly without sun," continued the Bushman.