Discrete generation cycles in the tropical moth Opisina arenosella.

摘要

Insect populations with discrete generation cycles (DGCs) have been rarely encountered in the tropics. Among the few known species, spatially segregated coastal populations of Opisina arenosella, the coconut caterpillar, have been shown to follow DGCs during outbreaks in Sri Lanka. Climatic parameters are known to be important in regulating generation cycles in insect populations. However, unlike temperate conditions, the tropics are characterized by high spatial heterogeneity in climate, which prompted the present investigation on generation cycles of populations of O. arenosella occurring in interior dry landscapes of the Indian peninsula. Two spatially isolated populations were regularly sampled for two years (July 1999 to July 2001) and data were subjected to time series analysis to determine periodicity, if any, in the occurrence of different developmental stages of the population. Results showed that populations followed DGC with a periodicity of approximately one generation, and further, correlations showed that there was a definite lead/lag in the peaks of different developmental stages, which closely correspond to the developmental period of different stages of the insect. The findings suggest that discrete cycles of O. arenosella may not be related to seasonality. The importance of generation cycles with respect to pest management has also been discussed..