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The population trend of three milkweed bugs,Spilostethus pandurus (Scop.),Spilostethus hospes (Fabr.) andCaenocoris nerii (Germar) are studied in relation to climatic condtions over a period of two years on their principal hostCalotropis gigantea (L.). Of these milkweed bugs.Spilostethus pandurus is and occasional pest of several food and cash crops in India. All the three species are noted on the milkweed throughout the year. Their abundance shows regular seasonal variation.Spilostethus pandurus andCaenocoris nerii are abundant during the hotter months (March-August) and contrastinglySpilostethus hospes is more numerous during colder seasons (January–February and October–December). The variation in the population due to environmental factors is statistically highly significant. Of the various environmental factors maximum temperature is an important limiting factor in the population levels and distribution of all these three species. |
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