Abstract

In teak plantations at Nilambur, Kerala, Hyblaea puera Cramer (Lepidoptera, Hyblaeidae) caused one or two waves of epidemic defoliation between late April and July, followed in some years by isolated, lighter defoliation between August and November. The insect was absent at other periods, although with a 3-week life cycle it can theoretically pass through several generations per year. The temporal and spatial distribution of infestation and certain behavioural characteristics of population gave evidence of short-range migration of newly emerged moths. In a model proposed for population dynamics of H. puera, no diapause occurs and a residual, non-migratory population exists in natural forests during the non-epidemic period. With the onset of general flushing of teak in February-March, the population starts building up and when a critical density is reached, migratory behaviour is triggered. Migration facilitates exploitation of new food sources and escape from larval parasites