Field studies in Western Samoa showed that almost 40% of Aedes polynesiensis larvae were parasitized by the gregarine Lankesteria culicis. Adult trophozoites invade epithelial cells lining the gut of larvae and gametocyst formation and maturation occur in the Malpighian tubules of the pupa. The infection appeared to be associated with permanent larval habitats viz, tree-holes and crab-holes. Two companion species A. samoanus and A. aegypti were also examined. None of the 946 samoanus collected were infected and only 1 out of the 325 aegypti examined contained the parasite.