Man and Nature 407 



scale insects, tlie prospects for the ultimate control of these 

 pests in this way are promising. 



In Hawaii the ravages of the sugar-cane weevil, wliicli 

 bores its destructive way into the sugar canes, have been ma- 

 terially reduced by the introduction of a pai'asitic fly from 

 British New Guinea. Anotlier dread enemy of the Hawaiian 

 sugar planter is a little bug known as a "leaf hopper," which 

 was probably introduced from Australia about 1898. Soon 

 it was doing so much damage that the production of one large 

 plantation fell from 10,954 tons in 19U4 to 82G tons in 1906. 

 Meantime however the expert entomologists were on the trail 

 of the leaf hopper, pursuing it with jjarasites, furnished by 

 Australia. Their first attempts were failures, but these were 

 shortly followed by success. The parasites throve and soon 

 had the pest so well under control that this same plantation 

 yielded in 1907 11,630 tons of sugar. 



But the path of the experimental entomologist is by no 

 means always strewn with roses. There is in P^urope a fly 

 which parasitizes the caterpillar of the brown-tail motli, which 

 is covered with poisonous hairs. These hairs are sufificiently 

 poisonous to produce a serious eruption in man known as the 

 "brown-tail rash." Now there is in this country a variety 

 of the same species of parasite, which does not attack the 

 brown-tail's larva because apparently it is susceptible to the 

 poison of the latter 's hairs. Upon the discovery of these facts, 

 the European race was imported into the United States in 

 large numbers, and in the following year was found to be at- 

 tacking the caterpillars of the brown-tail moth. The enthusi- 

 asm of the entomologists aroused by this discovery was short 

 lived however, for the next year none of the caterpillars was 

 attacked. The explanation of this unfortunate state of af- 

 fairs proved to be that the foreigners were interbreeding with 

 the natives, and their offspring had lost the immunity enjoyed 

 by their European cousins. 



In 1796 an epidemic broke out among Pennsylvania cattle, 

 which was traced to a herd from South Carolina which al- 

 though healthy themselves were infectious to olher animals. 

 In 1868 Texas cattle shipped into Illinois and Indiana brought 

 disease into these states causing such extensive ravages that 

 the eastern states became alarmed, not only because of the 

 loss to stockmen themselves, but because of dreaded injury 

 to human health from the consumption of tliseased meat. 



The cause of all this trouble is a protozoan, parasitic in the 

 blood of cattle, where it produces a disease somewhat sim- 

 ilar to malaria in man; while the disseminator of infection is 

 the cattle tick, tlie life history of which is briefly as follo\ys. 

 After gorging itself upon the blood of its unfortunate vie- 



