FACTORS AFFECTING THE TIME OF THE CREPUSCULAR MATING FLIGHT AND DURATION OF MATING OF THE MOTH ONCOPERA ALBOGUTTATA TINDALE (LEPIDOPTERA: HEPIALIDAE)

Field observations were made on a large population of Oncopera alboguttata at Ebor N.S.W. in order to investigate factors affecting the timing of the crepuscular mating flight and the duration of mating. The onset of the female flight lags about 10–14 minutes behind that of the male flight. The already flying males do not stimulate females to take-off and their presence therefore does not influence the timing of the female flight. The median time of take-off for either sex is influenced by differences in cloud cover but is less affected than would be expected if light intensity were the sole determinant of take-off time. The time at which the first males take to flight is more closely related to light intensity. Mating durations varied from 5–35 minutes. Those pairs which began mating in the early part of the flight period mated for longer than those which paired later in the flight period. This behaviour has the effect of keeping already mated females from taking flight while the male flight is continuing.