The microfilariae of Brugia malayi can be identified by several characteristic morphologic features: they measure 175 to 250 micrometers in length on Giemsa-stained peripheral blood smears, have a sheath which often (but not always) stains deep pink with Giemsa, and they have a tapered tail with a terminal and subterminal nucleus. There is a significant amount of space between the 2 nuclei.