Page:Popular Science Monthly Volume 81.djvu/50

44 he has killed over 40,000 flies (about four quarts) inside of twenty-four hours in a barn where flies were very numerous.

The terrible scourge of Africa known as sleeping sickness is caused by a protozoan parasite known as Trypanosoma gambiense, and is transmitted by the bite of a species of fly, Glossina palpalis. In our own southern states the disease known as "pink eye" is disseminated by a minute fly of the genus Hippelates.

 showing a manure heap where thousands of house flies breed.

Malaria has been known ever since 400 B.C. in southern Europe, and from the records it must have been present in Connecticut for about 250 years, though rot generally distributed here, nor did it appear in the form of an epidemic until about 1860, when it broke out in the southwestern corner of the state and spread gradually during the next twenty years until the entire area of the state was involved. It is thought that soldiers returning from the Civil War brought it from the south.

The cause of malaria was formerly thought to be gases or foul emanations from swamps, and it was in 1881 that Laveran, a French army surgeon, discovered in the red corpuscles of human blood a protozoan parasite, which he named Plasmodium malariæ. Though the mosquito was suggested by King in 1882 as a possible agent in