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Journal of Entomological Research
Year : 1997, Volume : 21, Issue : 1
First page : ( 17) Last page : ( 23)
Print ISSN : 0378-9519.

Population dynamics of the water bug, Diplonychus indicus Venk. & Rao, a bioagent in mosquito breeding pond

Jeyanthi Mary*, Venkatesan P.

Department of Zoology, Loyola College, Nungambakkam, Madras-600 034, Tamil Nadu (India).

*Present address: Department of Zoology, Women's Christian College, Madras-600 006, Tamil Nadu (India).

Accepted:  20  September,  1996.


Population dynamics of Diplonychus indicus Venk. & Rao studies from October 1990 to November 1991 revealed fluctuations with the variations in rainfall. The meteorological parameters showed that rainfall was minimum (0.3 mm) in October 1990 and maximum (131 mm) in November 1990. The relative humidity rmged from 65 to 85 per cent during the experimental period. Atmospheric temperature fluctuated between 24.T°C in November 1990 and 41.3°C in May 1991. Population size of D. indicus wps highest (190) in December 1990 and was very low (45) in September 1991. In December 1990, January and August 1991, encumbered males outnumbered the males than in other, months. Among the, post-embryonic stages, the fourth and fifth nymphal stages occurred throughout the year. But, the first and second nymphal stages were poorly represented. Sex-ratio revealed male dominance in the population. The population of this water by varied considerably even when the pH value showed only a marginal variation from 7.03 to 7.57. The chlorinity of water samples collected from study site, Cooum river, showed a wide range of fluctuations from 452 ppm in July, 1991 to 4068 ppm in June, 1991 and during the remaining period from 565 to 2488 ppm. The bug, probably, adapted to such variations in salinity.


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