Abstract
Studies were made on the development of Babesia gibsoni in the midgut of the nymphal stage of the tick, Rhipicephalus sanguineus. Six hr after repletion, merozoites of B. gibsoni, free of erythrocytes, were observed in the midgut contents of the ticks. After that, within 24 hr, those merozoites were transformed into ring-forms which were relatively large ring 1-2 μm in diameter. Later, the ring forms developed into spherical forms which were somewhat elliptical in shape and 3-4 μm in diameter. Within 2-4 days, bizarre forms (5-6 μm in diamater) developed into elongated forms (5-6 μm in length). About 5-6 days after repletion, large round or elliptic zygotes (7-9 μm in diameter) were observed in the ticks gut.
