By looking one could see the creatures sitting on the under side of leaves with their heads stretched out waiting to attack anything that went by.

As wayfarers there could not have been numerous, I wondered what they had lived on for the last few thousand years.

By the way, I found that paraffin, of which we had a small supply for our hand-lamps, rubbed over all exposed surfaces, was to some extent a protection against these blood-sucking worms and the gnats, although it did make one go about smelling like a dirty oil tin.
During the day, except for the occasional rush of some great iguana or other reptile, and the sound of the wings of the flocks of wildfowl passing over us from time to time, the march was deathly silent.

But at night it was different, for then the bull-frogs boomed incessantly, as did the bitterns, while great swamp owls and other night-flying birds uttered their weird cries.

Also there were mysterious sucking noises caused, no doubt, by the sinking of areas of swamp, with those of bursting bubbles of foul, up-rushing gas.
Strange lights, too, played about, will-o'-the-wisps or St.Elmo fires, as I believe they are called, that frightened the Zulus very much, since they believed them to be spirits of the dead.