INSECT PESTS 39 



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 bird-shot ; 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 Pan- 

 handle 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 Con- 

 cepcion, 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 also we 

 are not as yet able to fathom, these insects are for the 

 most part strictly limited by geographical and other 

 considerations. The war against what Sir Harry 

 Johnston calls the really material devil, the devil of 

 evil wild nature in the tropics, has been waged with 

 marked success only during the last two decades. The 



