|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1996 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1995 : ¥1,400,000 (Direct Cost : ¥1,400,000)
The aim of this research is to clarify the interactions between kleptoparasitic spiders and their host as well as the interactions between kleptoparasitic spiders.
Field research was conducted in Nangusuku, Shoshi and Nakijin castle in Okinawa prefecture where kleptoparasitic Argyrodes spiders were abundant.
The main results and discussions are as follows.
1) Multiple regression analysis showed that number of A.flavescens on the host web is related to food conditions of host spiders. Field experiments, in which all A.flavescens were removed from the web, revealed that the number of that species seems to be near the level of carrying capacity at the web.
2) Intraspecific competition for a particular site within a web was ovserved in A.flavescens. That is, larger individuals tended to occupy the advantageous site for prey capture. Individuals immigrating into the web from which all individuals had been removed were relatively small in body size. This suggests that smaller individuals wre banished from the web through intraspecific competition. It was shown, however, that the intensity and the way of intraspecific competition varied depending on the food conditions and population density.
3) Weak interspecific competition was found between A.flavescens and A.bonadea, that is, the presence of the former species had a negative effect on the number of the latter species.
4) The effect of the number of Argyrodes spiders upon the frequency of web-site relocation of host spiders was not recognized. It was estimated that A.flavescens steals 19% of prey mass captured by the host spider. Thus, no evidence was obtained for the negative effects of Argyrodes spiders upon host spiders.