ped for wood
at some little settlement. Across the river to the west lay the level,
swampy, fertile wastes known as the Chaco, still given over either to
the wild Indians or to cattle-ranching on a gigantic scale. The broad
river ran in curves between mud-banks where terraces marked successive
periods of flood. A belt of forest stood on each bank, but it was only
a couple of hundred yards wide. Back of it was the open country; on
the Chaco side this was a vast plain of grass, dotted with tall,
graceful palms. In places the belt of forest vanished and the palm-
dotted prairie came to the river's edge. The Chaco is an ideal cattle
country, and not really unhealthy. It will be covered with ranches at
a not distant day. But mosquitoes and many other winged insect pests
swarm over it. Cherrie and Miller had spent a week there collecting
mammals and birds prior to my arrival at Asuncion. They were veterans
of the tropics, hardened to the insect plagues of Guiana and the
Orinoco. But they reported that never had they been so tortured as in
the Chaco. The sand-flies crawled through the meshes in the mosquito-
nets, and forbade them to sleep; if in their sleep a knee touched the
net the mosquitoes fell on it so that it looked as if riddled by
birdshot; and the nights were a torment, although they had done well
in their work, collecting some two hundred and fifty specimens of
birds and mammals.

Nevertheless for some as yet inscrutable reason the river served as a
barrier to certain insects which are menaces to the cattlemen. With me
on the gunboat was an old Western friend, Tex Rickard, of the
Panhandle and Alaska and various places in between. He now has a large
tract of land and some thirty-five thousand head of cattle in the
Chaco, opposite Concepcion, at which city he was to stop. He told me
that horses did not do well in the Chaco but that cattle throve, and
that while ticks swarmed on the east bank of the great river, they
would not live on the west bank. Again and again he had crossed herds
of cattle which were covered with the loathsome bloodsuckers; and in a
couple of months every tick would be dead. The worst animal foes of
man, indeed the only dangerous foes, are insects; and this is
especially true in the tropics. Fortunately, exactly as certain
differences too minute for us as yet to explain render some insects
deadly to man or domestic animals, while closely allied forms are
harmless, so, for other reasons, which