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Volume 22 (1969)
- Issue 2 Pages 27-
- Issue 1 Pages 1-
Volume 22, Issue 2
Displaying 1-4 of 4 articles from this issue
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Jun-ichi AOKI1969 Volume 22 Issue 2 Pages 27-30
Published: December 25, 1969
Released on J-STAGE: December 19, 2008
JOURNAL FREE ACCESSDownload PDF (131K) -
Kazuyoshi MIYASHITA1969 Volume 22 Issue 2 Pages 31-34
Published: December 25, 1969
Released on J-STAGE: December 19, 2008
JOURNAL FREE ACCESSPlexippus setipes was reared under constant temperature (27-28°C) and photo-peried (16 hours each day), and the following results was obtained.
1. The spiders moulted 5 to 6 times before they reached adulthood.
2. Durations of days in each instar were greatly affected by the food condition, the duration was shortened when feeding interval became short.
3. Total number of days required for the development from the first instar to adult was 110-200 days, excepting the period of immature nymphal stage staying in egg-sac.View full abstractDownload PDF (134K) -
Ranks of Dominancy Among Species In a CommunityShigeyoshi HONDA1969 Volume 22 Issue 2 Pages 35-39
Published: December 25, 1969
Released on J-STAGE: December 19, 2008
JOURNAL FREE ACCESSHONDA, Shigeyoshi (Department of Zoology, Faculty of Science, Kyoto Uni-versity) On the method for quantitive analysis of web spider community (I), Ranks of dominancy among species in a community.
A method for finding out the dominant species in a web spider community based on the line transect sampling was proposed.
The rank of dominancy is estimated from the relative size of the mean space occupied by each species in unit space surveyed (1m in width, 5m in height and 1m in distance) along a survey route. The mean space occupied by a species (Os) is obtained by:
OS=OI•DS where OI and Ds are the mean value of individual space occupation and mean number of individuals per 1m3 respectively.
As a convenient method, the index method was also proposed in which the index of specific space occupation (IOS), instead of Os, obtained by the following formula is used:
IOS=IOI+IDS where IOI=log OI and IDS=log DS=0.699 (NSC-8) in which NSC is the density class taking the unit based on the logarithm of the population density.
As a result of application the method to the web spider community in an artificial forest of Cryptomeria, the ranks of dominancy of the species in this com-munity were estimated as: (1) Nephila clavata, (2) Cyclosa sedeculata, (3) Theridion takayense, etc.View full abstractDownload PDF (188K) -
Tetsuzô HAMAMURA1969 Volume 22 Issue 2 Pages 40-50
Published: December 25, 1969
Released on J-STAGE: December 19, 2008
JOURNAL FREE ACCESSFor the purpose of understanding of spider's role in paddy fields, this study was carried out from 1966 to 1968 at Utsunomiya, Tochigi Prefecture, Japan. Popu-lation density of spiders was examined in two paddy fields of Mine and Ishii Town. Seasonal fluctuations of all spiders in two paddy fields are shown in Fig. 2 and 3. In every cases, just after the rice-planting season, numbers of spiders found in these paddy fields, were few. Then they gradually increased up to autumn. Maximum number of spiders was about 90/m2 at the Mine field (Fig. 3). By the insecticidal applications the spider population was scarcely influenced in early stage, however the number of spiders decreased in late stage of rice plants.
Seasonal fluctuations of each main species are shown in Fig. 4-12. In the late stage of rice plants, the population density of main species in Ishii field where insecticides were sprayed by helicopter was low compared with that in Mine field where those were not done, but only the population density of Pirata subpiraticus kept exceptionaly high in the Ishii field as well as that in the Mine field.
Many species reached maximum density in October, that is, harvesting time of rice plants. On the other hand, leaf hoppers and plant hoppers reached the maximum density in September. Therefore the spiders in late season, do not serve enough as the natural enemy of these insect pests. But the maximum den-sity of Pirata subpiraticus emerged in August, in cases in which the density around June was high to some extent.
From these results, Pirata subpiraticus seems to be the most useful spider as predator to insect pests in paddy fields.View full abstractDownload PDF (532K)
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