Field observations of Ostrinia nubilalis eclosion and post-eclosion activity of females around their natal plants

The early part of the post-eclosion, pre-mating period were examined under field conditions for Ostrinia nubilalis. Post-eclosion behavior of 25 and 21 females during the first and second flight periods were observed until they left their natal site. Summer generation larvae were reared under field conditions and the timing of adult eclosion was observed. Eclosion occurred at two times during the day, peaking before dawn and before dusk; 46% of females and 56% of males eclosed during the morning period and the rest eclosed during the evening period. After eclosion, females spent 30-60 min expanding their wings. Their typical behavior was to remain calmly on their natal site. None of the females exhibited calling behavior before leaving. All females left their natal sites sometime before dawn. The probability of leaving increased with time. Leaving rates were not significantly different between females of the first and second flight. These field observations indicate that females have several possibilities for pre-mating movement, which might allow females to move out from their natal field before mating. In addition, we also discuss the influence of pre-mating movements in relation to the rate of Bacillus thuringiensis (Bt) resistance evolution.