After a cat is inoculated with infective third-stage larvae from mosquitos, the molt from the third to fourth stage occurs about 8 or 9 days later (Schacher, 1962a). The molt from fourth-stage larvae to adults occurs about 23 days after infection in the case of male worms and about 27 days after inoculation in the case of female worms. Microfilariae appear in the blood about 60 days after infection (Edeson et al., 1960; Schacher, 1962a). The females do not reach maximal length until about 120 days after infection; the males reach maximal length about 60 days after infection. The mean prepatent period in cats is 69 days; but it may take up to 96 days before a patent infection develops (Denham, 1974). Ewert and Singh (1969) found that experimentally infected cats first became microfilaremic about 10 weeks after infection. Microfilarial count were around 3 or 4 microfilariae per microliter of blood. Adults worms are capable of living in some cats over two years.