PHYLUM ARTHROPODA — CLASS INSECTA 341 



the past thirty or forty years has been made in the field of medical 

 entomology. Diseases such as malaria, yellow fever, typhus fever, 

 African sleeping sickness, bubonic plague. Rocky Mountain spotted 

 fever, tularemia, and elephantiasis are now known to be insect borne. 

 Much remains to be done in this new entomological field. 



After man has produced his crops and harvested them for use, 

 he finds many insects ready to take their toll from these concen- 

 trated products. The "board bill'* of the insect pests of stored 

 foods annually amounts to about four times the cost of all higher 

 institutions of learning in this country. Insects belonging to the 

 orders Coleoptera and Lepidoptera are the main offenders. The pea 

 weevil, bean weevil, granary weevil, and confused flour beetle feed 

 upon and damage practically all kinds of grains and seeds and their 

 products. Much damage is also done to the same products by such 

 species as the Mediterranean flour moth and the Indian meal moth. 

 Practically all pests of stored foods are world-wide in their distribu- 

 tion, which makes it difficult to ship food products long distances 

 or store them for future use without running the hazard of insect 

 damage. 



Many insects have taken up their abode with man, living upon 

 his upholstered furniture, clothing, furs, and rugs. Great losses are 

 suffered annually by the producers of clothing, as well as in the 

 homes, due to clothes moths. Termites also attack the wooden parts 

 of dwellings, even furniture and books. The tobacco beetles and 

 drugstore beetles live upon tobacco products, home furniture, and 

 many drugs. 



Useful Insects 



Fortunately not all insects are our enemies. Many species are 

 allies of man in the struggle against the injurious insects, as well 

 as in many other ways. 



Everyone knows that honey is produced by the honey bee and 

 silk by the silk moth, but there are many people who do not know 

 that certain insects produce shellac, the pigment cochineal, tannic 

 acid, formic acid, cantharidin or "Spanish fly," inks and dyes, and 

 beeswax. In India a small scale insect, Tachardia lacca Kerr, lives 

 on trees and produces a secretion that forms a layer over the 

 branches. This substance, shellac, is removed by the natives in 



