PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 353 



ism is still unknown, and may probably be of ultra-microscopic 

 size. Even as early as 1881 Dr. Finlay, of Havana, had sug- 

 gested that mosquitoes might be responsible for yellow fever, 

 but his speculations had met with little approval. Not until the 

 American occupation of Cuba did this theory secure an experi- 

 mental test by a commission of army surgeons headed by Major 

 Reed. The work of 1900 and 1901 cost the hfe of Dr. Lazear, 

 but led to an almost perfect demonstration of the agency of 

 mosquitoes of the genus Stegomyia as the bearer of the yellow 

 fever parasite, and made possible the conquest of yellow fever 

 in Havana and the Gulf ports and the building of the Panama 

 Canal. 



Since 1900 the number of known protozoan diseases has 

 been increasing at a rapid rate, until the protozoa divide the 

 doubtful honors with their vegetable rivals, the bacteria, as dis- 

 ease producers in man and beast. It may well be that the pen- 

 dulum has swung too far in this direction and that the protozoa 

 are held responsible for more crimes against life and health than 

 they have really committed. But there can be no question that 

 they are a very important factor in disease production ; and it is 

 equally certain that this discovery is one of the greatest prac- 

 tical scientific achievements of the quarter century we are con- 

 sidering. What its future significance to the human race will 

 be w^e can hardly begin to estimate as yet. 



ECONOMIC ENTOMOLOGY 



Not all protozoan diseases are carried by insects, but a suffi- 

 cient number to have furnished a tremendous incentive to the 

 study of bloodsucking insects and their arachnid relatives. 



Foreign invasion by insects injurious to crops has proved 

 another important stimulus to entomological study. In 1893 the 

 San Jose scale was discovered in the eastern part of the United 

 States, already widely distributed through the stock shipments 

 of two New Jersey nurserymen, who had unwittingly brought 

 it from California, where it had gained an earlier foothold. The 

 results were described by Howard in 1900: "In 1897 and 1898 

 it was seen that there was hardly an important fruit-growing 



