1 The defoliator beetle, Mesoplatys ochroptera Sta l, is a serious pest of the legume tree sesbania ( Sesbania sesban (L.) Merrill) in agroforestry systems in southern Africa. The survival of the overwintering stage of M. ochroptera and post- emergence longevity and fecundity of adults in sesbania fallows in eastern Zambia were quantiÆed. 2 Only adult M. ochroptera survived during the winter (May±August) and the dry season (September±October) hidden under weeds, plant litter, in soil cracks and under rocks. During these periods, some beetles were occasionally found feeding on S. sesban , particularly in natural stands in humid areas. The adults were para- sitized by the braconid Perilitus larvicida van Achterberg at a rate of 8.5±16.4%. The beetles stayed in the winter refuges for up to 210 days and emerged with the Ærst heavy rains in October±November. The effective survival of beetles over- wintering in an insectary was 18.1% in 1998 and 37.7% in 1999, and that of bee- tles overwintering in the Æeld was estimated at 0.4 and 2.8% in 1998 and 1999, respectively. 3 The post-emergence longevity and oviposition period of females in the insectary was 14±31 days and 5±29 days, respectively. The post-emergence fecundity varied from 87 to 783. 4 It is concluded that the serious M. ochroptera infestation observed every year following the rains is due to synchronous emergence of overwintered resident adult populations and their high capacity for reproduction on many species of Sesbania . Recommendations for pest management in sesbania planted-fallows are given.