Brugia malayi, along with Brugia timori and Wuchereria bancrofti, causes lymphatic filariasis. The microfilariae are found in blood, usually between the hours of 10 pm and 2 am (nocturnal periodicity), and 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.