n. (pl. microfilariae) the motile embryo of certain nematodes (see filaria). The slender microfilariae, 150–300 ?m in length, are commonly found in the circulating blood or lymph of patients suffering an infection with any of the filarial worms, e.g. Wuchereria. They mature into larvae, which are infective, within the body of a bloodsucking insect, such as a mosquito.