Comparative susceptibility of Culex tarsalis, a Nopheles franciscanus, and Culiseta inornata (Diptera: Culicidae) to Plasmodium relictum (Haemosporidia: Plasmodiidae)

Repeated laboratory attempts failed to infect Culiseta inornata (Williston) and Anopheles franciscanus McCracken with Plasmodium relictum as efficiently as Culex tarsalis Coquillett controls. Of 210 An. franciscanus that imbibed a replete meal from a parasitemic canary, two were found with oocysts and none with sporozoites. Of 112 Cs. inornata similarly fed, seven contained oocysts and one contained sporozoites. In contrast, of 94 Cx. tarsalis tested, 80 (85%) were found with oocysts, thus confirming that this mosquito is a suitable host of P. relictum . Lack of An. franciscanus and Cs. inornata with sporozoites precluded transmission studies and indicated that these species do not play a major role in the maintenance of P. relictum during fall and winter in the Sacramento Valley, Calif.