_Malaria-Transmitting Mosquitoes_.—In the United States, _Cellia albimana_, _C. argyrotarsis_, _Anopheles crucians_, _A. quadrimaculatus_ and _A. pseudopunctipennis_ are efficient transmitters of malaria. Rather remarkable is the experience of Beyer in New Orleans that _A. crucians_ will only transmit _P. falciparum_ while _A. quadrimaculatus_ will transmit _P. vivax_ and _P. malariae_, but not _P. falciparum_. Further experiments have shown that _A. crucians_ will transmit _P. vivax_ as well as _P. falciparum_. As showing the uncertainty attaching to the question of a certain anopheline species being efficient hosts for malaria may be cited the case of _A. punctipennis._ This species has been frequently reported as incapable of transmitting malaria and quite recently Mitzmain reported experiments on 219 females of the species which had fed on crescent containing blood and which were dissected from three to thirty-eight days after such feedings with negative findings in stomach and salivary glands. Furthermore, these mosquitoes failed to transmit malaria to healthy persons. Control experiments with _A. quadrimaculatus_ and _A. crucians_ were successful. In June, 1916, Dr. King reported 33% of positive findings after dissection of _A. punctipennis_ which had fed on malignant tertian cases and 85% of success where the man bitten had benign tertian malaria. These results showed as high a degree of success as that obtained with the control _A. crucians_ and _A. quadrimaculatus_. From the above it must be evident that there are other factors involved besides that of the host species as both Mitzmain and King are expert epidemiologists. A species which may be the chief transmitter in one country may be unimportant, though present, in another country. Thus _Cellia albimana_ is the chief malarial transmitter of Panama although _C. argyrotarsis_ is present. In Brazil the conditions are reversed, probably due to _C. albimana_ thriving best where slightly brackish pools of standing water abound, as in Panama. In the Philipines _A. febrifer_ seems the important transmitter. It freely enters houses and is a vicious biter. In India the species which seem most active in transmitting malaria are _Myzomyia culicifacies_ and _M. listoni_; while in Africa, _M. funesta_ is very efficient. In Europe _A. maculipennis_ and _A. bifurcatus_ are important. The following species of anophelines selected from the different genera are important transmitters of malaria. _Anopheles maculipennis_.—Wings with four spots located at bases of both forked cells and of second and third longitudinal veins. No costal spots. Palpi yellowish brown and unbanded. Legs unbanded.