- 衛生動物 (ISSN:04247086)
- vol.24, no.1, pp.83-88, 1973
Four tanks, labeled A, B, C, and D, containing 750 liters of water, were placed outdoors near the laboratory. Breeding of Culex pipiens pallens was found in each tank in early June, 1972. Twenty guppies, or 10 mature pairs, were introduced in two of the tanks, B and C, on 9 June 1972. Tank B was then treated with fenitrothion 1ppm, tank C remained untreated. Tank D was treated with fenitrothion 1ppm on the same day, and tank A, the control tank, received neither guppies nor fenitrothion. The observation for each tank was conducted using a ladle to count the larvae and pupae densities every two or three days. Also counts of total number of egg rafts on the water surface were made on the same day. These observations were made until the end of September. According to the results, the larvae and pupae dramatically disappeared on the fourth day after fenitrothion treatment in both tanks B and D. In the case of tank D, the chemical treatment had to be repeated five times during a two-month period due to the outbreak of larvae every 10 or 20 days. Tank B, however, received no additional chemical treatment after the initial treatment because of the presences of the guppies. A number of pupae was observed for three weeks after introduction of guppies to tank C, but all pupae had disappeared by the end of this period. More than 100 rafts a day of oviposition were observed in tanks A and D. However, no rafts were recognized from tanks B and C, except for very few days during the peak time of oviposition activity of mid-summer. As Part II of the present report series showed, these egg rafts were eaten by guppies in each tank. Thus, in tanks B and C no adult mosquitoes emerged throughout the summer season.