In systematic captures performed at the Serra dos Órgãos National Park, in Rio de Janeiro, Brazil, from October 1980 through September 1982, the preference of sandflies to feed at sunset or at night was confirmed. During the day sandflies were found to bite only when the weather was cloudy or during the dark moments that precede rainstorms which are frequent in summer. When three periods of captures were compared - morning (6 to 8 a.m.), sunset (5 to 7 p.m.) and night (7:30 to 9:30 p.m.) -, L. ayrozai and L. hirsuta behaved similarly, feeding mostly at sunset, while L. shannoni was more eclectic and L. fischeri preferred to bite at night. In 2-hour captures performed during 24 consecutive hours the peaks of hematophagic activity were different for L. ayrozoi and L. hirsuta: from 11 p.m. to 2 a.m. for the former and 6 to 11 p.m. for the latter. However, both can feed at any hour if conditions of temperature and humidity are favourable.