A third form, Microfilaria diurna, is found in the larval stage in blood, but only in the daytime.
2
Microfilaria nocturna swarmed in the blood at night-time and disappeared from the peripheral circulation during the day, hiding away in the large vessels at the base of the lungs and of the heart.
3
They, however, show no periodicity, and are found continuously both by day and by night; and their larval forms are termed Microfilaria perstans.