Studies on sympetrum frequens odonata libellulidae nymphs as natural enemies of the mosquito larvae anopheles sinensis in rice fields 4. prey predator relationship in the rice field areas
Urabe, K.; Ikemoto, T.; Takei, S.
Medical Entomology and Zoology 41(3): 265-272
The prey-predator relationship between larvae of the mosquito Anopheles sinensis and nymphs of the dragonfly Sympetrum frequens in rice field areas was investigated in the suburbs of Omiya City, Japan, during the period from June to July of 1979 (for Area-A and the whole area) and 1980 (for Area-B), and July 1986 (for the whole area). The average density of S. frequens nymphs in Area-A (210a) and Area-B (430a) was 23-41/m2 and 2-6/m2, respectively. On the contrary, densities of An. sinensis larvae were very low in Area-A and high in Area-B. In both the areas, the density of S. frequens nymphs in a rice field was much different from those in neighbors. The precipitin test of the gut content of S. frequens nymphs with antiserum against An. sinensis larvae indicated that the proportion of An. sinensis larvae preyed by S. frequens nymphs was estimated to be 83.3 to 100% in Area-A and 0 to 87.5% in Area-B. The density of S. frequens nymphs in the whole area (97 ha) was about 4/m2 during the first half of June of 1979 and 1986. The distribution of nymphs in the area was contagious. On 17 June 1979, 18.2% of S. frequens nymphs had detectable An. sinensis antigen in the gut, and 39% of An. sinensis larvae were estimated to be preyed by S. frequens nymphs during the day. An. sinensis larvae in the survey area could be controlled effectively by S. frequens through appropriate management of rice fields.