著者

NAKASUJI FUSAO YAMANAKA HISAAKI KIRITANI KEIZI

出版者

日本昆虫学会

雑誌

昆蟲 (ISSN:09155805)

巻号頁・発行日

vol.41, no.2, pp.220-227, 1973-06-25

被引用文献数

1

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Some experiments and field observations were conducted in 1970 and 1971 in Ino, Kochi, to assess the effect of micryphantid spiders, mainly Oedothorax insecticeps, upon the larval colony of the tobacco cutworm, Spodoptera litura. In the taro field, the density of the micryphantid spider was high in the rainy season, i.e. June to early July, but it decreased rapidly in early July. The low density was maintained during the summer season, although the spider was very abundant in wet places overgrown with weeds. On the basis of the functional response of the spider, it was estimated that the maximum number of hatchlings which can be eaten by a spider was 96 individuals during the 1st instar. Survivorship curves of the spider-free larval colonies in cages of nylon gauze were compared with those of colonies exposed to the spider in the cages. Sixty and 18 per cent of mortality were observed by the next day of hatch in exposed and spider-free cages, respectively. Of 60 per cent mortality, only 4 per cent was accounted for by the actual predation which was assessed by the number of head capsules left on the taro leaf. Since 18 per cent of hatchlings were dead in spider-free cage, remainder, i.e. 60-18-4=38 per cent, was loss by larval dispersal out of the leaf induced by the spider's attack. Egg masses composed of various numbers (100-900) of eggs were placed on taro plants, and changes in number were followed during the 1st instar. In the period from late June to early July when micryphantid spiders were abundant, the survival rates of 1st instar larvae were 2-3% regardless of the number involved in the colony up to 900 individuals per colony. Taking consideration of the maximum number of prey could be eaten by a spider, i.e. 96 individuals, almost all of the hatchlings would be killed indirectly by the disturbing effect of spiders.

著者

TAKAHASHI Yohzi KIRITANI Keizi

出版者

日本応用動物昆虫学会

雑誌

Applied entomology and zoology (ISSN:00036862)

巻号頁・発行日

vol.8, no.4, pp.220-226, 1973-12-25

被引用文献数

2

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Relative toxicity of 14 insecticides was examined by the topical application. Test animals were two rice pests : Nephotettix cincticeps and Chilo suppressalis, and their predators : Lycosa pseudoannulata and Conocephalus maculatus. The relative toxicity of insecticides was expressed in terms of the ratio of LD50 of predators/LD50 of insect pests. Among four carbamates, carbaryl was least toxic to L. pseudoannulata and C. maculatus. Of the organophosphates used, fenitrothion, pyridafention and tetrachlorvinphos were less toxic to L. pseudoannulata but were highly toxic to C. maculatus. C. maculatus, however, was very susceptible to six organophosphates. The toxicity of chlorophenamidine to L. pseudoannulata was as high as carbamates but was low to C. maculatus. The acute toxicity of cartap to L. pseudoannulata was low, i.e., 102.6 μg/g(LD50 after 24 hr), but all spiders were paralysed as low as at 10 μg/g and their recovery was postponed 8 days. The toxity of γ-BHC and methomyl to both species of predators were high : the values of the relative toxicity were far less than unity.