INTERACTION BETWEEN KLEPTOPARASITIC SPIDERS AND WEB-BUILDING SPIDERS.

本研究的目的是阐明盗寄生蜘蛛与宿主的相互作用以及盗寄生蜘蛛之间的相互作用。在冲绳县的南古苏古、Shoshi和Nakijin城堡进行了实地调查，那里有大量的盗窃寄生argyardes蜘蛛。主要研究结果和讨论如下。1)多元回归分析表明，黄丝蜘蛛在寄主蛛网上的数量与寄主蜘蛛的食物条件有关。现场实验表明，将所有黄花蒿从网中去除后，黄花蒿的数量似乎接近网的承载能力水平。2) a .flavescens在一个网络中对特定位点的种内竞争被观察到。也就是说，体型较大的个体往往占据捕食猎物的有利位置。迁移到所有个体都被移出的蛛网中的个体体型相对较小。这表明，较小的个体通过种内竞争被排除在网络之外。然而，种内竞争的强度和方式因食物条件和种群密度的不同而不同。3) a .flavescens与a .bonadea之间存在弱的种间竞争，即前者的存在对后者的数量有负向影响。4)银蛛数量对寄主蜘蛛迁址频率的影响尚不清楚。据估计，黄刺蛛会偷走19%的寄主蜘蛛捕获的猎物。因此，没有证据表明银蛛对寄主蜘蛛有负面影响。

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.