• K Thangavelu

      Articles written in Proceedings – Animal Sciences

    • Population dynamics of the dusky cotton bugOxycarenus laetus Kirby in relation to climatic variation (Heteroptera: Lygaeidae)

      K Thangavelu

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      The population trend of the dusky cotton bug,Oxycarenus laetus Kirby is studied for two years, on three principal hosts namelyAbutilon indicum, Sida acuta andThespesia populnea in relation to climatic variation. Population density varies significantly over the months as shown from the analysis of variance thereby indicating that the population build up is favoured by certain climatic factors. Regression analysis shows that variables such as temperature and relative humidity have very significant effect on the growth of the population. Peak population is recorded during hotter months March–July; the population is at its low ebb during colder winter months November–January. High temperature (35°C–40°C) and moderately high humidity (45–60%) seem to be the favoured climate for rapid growth of the population, whereas very high humidity adversely influence the population as indicated by the negative regression values obtained consistently in both years.

    • Influence of climate on the population of three milkweed bugs in South India (Heteroptera: Lygaeidae)

      K Thangavelu

      More Details Abstract Fulltext PDF

      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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