Comparative observations on the fate of ingested microfilariae of Brugia pahangi in 5 species (8 strains) of mosquitoes demonstrate that consistent failure of microfilariae to migrate in a species of mosquito to the thoracic muscles 1 hour or 1 day after being ingested indicates inefficient vector-ability. However, a high rate of migration of microfilariae does not necessarily indicate a high degree of vector efficiency, since this is not always correlated with successful later development of the filariae.
A high degree of successful migration occurred in Anopheles quadrimaculatus (2 laboratory strains) and in Aedes sollicitans (wild), while development to the infective larval stage occurred in 65 percent of the former but in none of the latter. About 50 percent of the ingested microfilariae reached the thorax in Ae. aegypti (2 strains) and in Ae. albopictus, but only about 2 percent in Culex quinquefasciatus (2 strains). Yet infective larvae developed in 4 percent of the latter species. They developed in 3 percent of Ae. aegypti queenslandensis, but not in a New Orleans strain of Ae. aegypti or in Ae. albopictus.