Release studies on the dispersion of the house flies and the blow flies in the suburban area of Kawasaki city, Japan

Abstract

A release study of the dispersion of the house fly, Musca domestica vicina, and the blow fly, Phaenicia spp. was conducted in the suburbs of Kawasaki city, near Tokyo, during September and October, 1959. The area selected for the purpose is considered to be typical suburbs of Japanese town which consists of farms and scattered residential areas. The flies used for release were obtained by netting wild adult flies at the site selected as the release point. The captured flies were fed for approximately 24 hours on the milk containing the radioactive phosphorus at the rate of 1 mc of radioactive material per 1l milk. The concentration used was confirmed by the laboratory investigation to be satisfactory for this test. Radioactive marked flies were released on the evening, when it become too dark for them to migrate. In order to recover the released flies, fly catch ribbons, fly catch papers and cage traps were used. Traps were set in thiry nine houses (except cage traps in twenty ones) within a area of 1, 000m radius from the release point. Trapped flies were examined for five times during a period of twenty three days after the release, the flies were divided by geiger counter to tagged and untagged ones. During the recovery operation, 28, 435 flies in total, were collected, the majority of them was found to be the house fly (68.6%) and blow fly (20.8%). Of 14, 250 marked house flies and 600 marked blow flies released, 456 (3.2%) and 25 (4.2%) flies were recovered by the traps, respectively. Of 456 radioactive tagged house flies, 347 (76.0%) and 454 (99.4%) were recovered at the release point and within a circle of 100m, respectively. Otherwise, each only one was trapped on the distance of 400 and 500m from the release point. In case of the blow flies, of 25 marked flies, 4 (16.0%) and 24 (96.0%) were recovered at release site and within a circle of 100m, respectively. Only a single fly was trapped on the distance of 700m. Because the density of trap was not the same for each trap-set distance, the number of recovered flies does not rightly represent the pattern of dispersion. Nevertheless, the result above stated would tell a tendency that large number of flies has moved within a circle of 100m from the release point. As shown in Fig.1, there are, adjacent to the release site, paddy field of 250m in width to the north, and a hill range of 20-30m in height to the south. To east and west, however, a high way runs. The fact that the majority of tagged flies recovered in the east and west directions would indicate that the dispersion was influenced strongly by the topographical condition. The daily change of the percent of marked flies recaptured at and near the release point is shown in Table 6. This result indicates that the decrease of recovery percent is abrupt at release site, becoming slowly at the adjacent sites.