2 ELEMENTARY ENTOMOLOGY 



is now known to carry typhoid fever and probably various intestinal 

 disorders, to which a large part of our infant mortality is due ; 

 and it has been well said that, during the Cuban War, probably 

 more American soldiers were killed through the agency of flies 

 carrying typhoid germs than by Spanish bullets. 



Injury to crops. In their economic relations the insects affect- 

 ing crops are by all odds of the most importance, many of them 

 causing a loss of several million dollars a year to the farmers of the 

 United States. The boll weevil destroys over $25,000,000 worth 

 of cotton in Texas and Louisiana alone, and 10 per cent of the 

 wheat crop of the entire country, valued at $60,000,000, is usually 

 destroyed by insect pests. It has been estimated by competent 

 authorities that i o per cent of the total value of the farm products 

 of the United States is annually lost by the ravages of insect 

 pests, amounting to nearly $800,000,000 per annum. 



Injury to domestic animals. Domestic animals are affected by 

 various insects, such as the warble, or ox-bot, and the screw worm, 

 which affect cattle, the sheep maggot, and many others, in- 

 cluding the ticks, which carry Texas fever and other diseases ; so 

 that the annual loss to live stock through insects is estimated at 

 $175,000,000 per year. 



Injury to household and stored goods. Housekeepers, manufac- 

 turers, and wholesale dealers must take into consideration the insect 

 life which affects all sorts of vegetable and animal products, and the 

 aggregate loss due to the insect pests of household and stored goods 

 must in the aggregate be a considerable item in domestic economy 

 and mercantile business. 



Productive insects. A few insects contribute directly to the 

 wealth of the world : the silkworm produces over $200,000,000 

 worth of silk annually, and the product of the busy honey-bee 

 amounts to over $20,000,000 per year in the United States alone. 



Beneficial insects. The direct relations of insects to mankind are 

 by no means the most important phases of their ecology. The role 

 of insects in the pollenization of fruits and flowers is fundamental 

 to the successful fruiting and perpetuation of a large proportion of 

 common plants. Again, a large number of insects prey upon or live 

 within the bodies of other insects, and constitute the most impor- 

 tant factor in the natural control of injurious species. Were it not 



