Although for years we have employed the same temperature (20°C.) for the incubation of anophelines infected with Plasmodium falciparum as for those infected with Plasmodium vivax, the results with the former parasite have not been satisfactory. In general the qualitative (per cent infection in the lot) and quantitative (number of cysts per infected stomach) infection of the mosquitoes with the falciparum parasite has tended to be lighter than in the case of vivax. Our justification for its continued employment has been the belief that at the lower temperature a less active metabolism tended to promote the longevity of the mosquitoes.
Consequently it appeared desirable to ascertain whether we could improve our results by incubation at a higher temperature, without an unfavorable mortality experience among the mosquitoes. Some preliminary observations had indicated that our mosquitoes satisfactorily withstood incubation at 28°C., therefore, this temperature was selected for comparisons.