10 INSECTS AND HUMAN WELFARE 



of the town in his report for 1914 stated that while during the 

 summer of 1913, prior to antimalarial work, the mills were 

 constantly short of help on account of the large numbers of 

 employees sick with malaria, during the summer of 1914 

 there had not been a day when the mills did not have suffi- 

 cient help. The manager of one mill stated that the improve- 

 ment in the regularity and efficiency of the employees had 

 been such that the amount ($1,000) which the mill had con- 

 tributed to the fund for anti-mosquito work was more than 

 regained in one month's operation." 



While these conditions are those of one of the most severely 

 affected districts, they are nevertheless repeated very gener- 

 ally throughout the entire area, more especially in the low- 

 lands, for the hilly or mountainous and better-drained 

 sections suffer less. 



As mentioned above, several species of Anopheles mos- 

 quitoes are concerned in the transmission of malaria in the 

 United States. Till very recently only one species. Anopheles 

 quadrimacidatus, has been thought to be of much importance. 

 Recent studies by Mitzmain and others show that this mos- 

 quito is the most important, as it may harbor the parasites 

 of all three types of malaria, but Anopheles punctipennis 

 (Fig. 3), a common, widespread species and Anopheles cru- 

 cians, a species abundant along the eastern coast of the 

 United States, may serve both as hosts for the tertian and 

 estivo-autumnal or subtertian forms. The ease and fre- 

 quency with which A. punctipennis may become infected 

 seems to vary greatly under different conditions and its 

 importance at least in northern districts is by no means 

 proved. 



All three species readily enter houses and are persistent 

 biters, although no more so than some other mosquitoes. 

 Both quadrimaculatus and punctipennis breed in stagnant 

 water, usually that of permanent nature containing algae or 

 other plant growth. They commonly occur near together, 

 with punctipennis usually more abundant. Larvae of the 

 latter species occur also rarely in temporary puddles and both 



