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Vertical Distribution of a Biting Midge, Culicoides oxystoma (Diptera: Ceratopogonidae) During Different Seasons in the Hooghly Estuary, Sagar Island, India
Published online by Cambridge University Press: 19 September 2011
Abstract
Vertical distribution of different larval instars and pupae of Culicoides oxystoma in different depths in the mud and sandflats of Hooghly estuary were studied in relation to soil temperature and moisture at three stations in and around Sagar Island during March 1983 to February 1984. Temperature recorded higher in 0–3 cm depth and gradually decreased in subsequent depths. During the last part of the pre-monsoon (May and June) season, moisture was recorded minimum in 0–3 cm depth and gradually increased in greater depths, but in other seasons (monsoon and post-monsoon) the results were just opposite. Larval and pupal population showed a peak during post-monsoon then gradually declined in pre-monsoon and early monsoon. They were mostly encountered throughout the year from 0–3 cm depth except during summer months (May, June and July). First and second instar larvae were only recorded from 0–3 cm depth. Third and fourth instar larvae were distributed in all the depths, maximum in 0–3 cm. Pupae were never encountered from deeper depth (6–9 cm). Temperature and moisture act as important factors to control the vertical distribution of larvae and pupae of this species.
Résumé
La distribution verticale des larves et des pupes de Culicoides oxystoma Tok. dans les profondeurs differentes (0–3 cm, 3–6 cm et 6–9 cm) de la boue et les plaines du sol de l'estuaire de Hooghly a été étudie par rapport à la température du sol et l'humidité à trois places autour de l'île de Sagar pendant Mars 1985 a Fevrier 1984. La température à la profondeur de 0–3 cm était la plus haute et diminuait vers le bas. Pendant le premousson (Mai et Juin) l'humidité était le minimum à la profondeur de 0–3 cm et augmente à la profondeur. Mais pendant le moussen et le postmousson la situation était l'opposite. Le pic de la population lavaire et pupaire a été atteint pendant le postmousson et puis decline pendant le premousson et le debut de mousson. A l'exception de l'été (Mai, Juin et Juillet) on les a rencontre toute l'année à la profondeur de 0–3 cm. Les larves de troiseème et quatrième stades ont été rencontréc à toutes les profondeurs; élles étaient la plus abondantes a 0–3 cm. Les pupes n'étaient jamais rencontré à la profondeur plus que 6–9 cm. La température et l'humidité jouent comme les facteurs determinants dans la distribution verticale des larves et des pupes de cette espèce.
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