Argyrodes fissifrons inhabiting webs of Cyrtophora hosts: Prey size distribution and population characteristics

In this field study we investigated the impact of Argyrodes fissifrons (Ara neae: Theridiidae) on two species of Cyrtophora spider hosts (Araneae: Aran eidae) by studying several aspects of its population and foraging. We exami ned (1) if natural population variations of A. fissifrons occur with differ ent web sizes of the hosts, (2) if A. fissifrons form long-term association s with particular hosts, and (3) if the size range of prey consumed by A. f issifrons overlaps with that of Cyrtophora hosts. Results from field survey s indicated that a positive relationship exists between the average number of A. fissifrons and the size of the host webs. The number of A. fissifrons per host web per day changed daily, indicating the daily occurrence of imm igration-emigration events. However, as inferred from monitoring marked A. fissifrons for 3 nights, some individuals form a long-term association with a particular host. The sex ratio, body size, and prey intake of A. fissifr ons spiders staying in particular hosts' webs during monitoring did not dif fer from those that left a web. A significant difference was found in prey size distribution between Cyrtophora hosts and A. fissifrons, and the avera ge prey size of the former was far greater than that of the latter. This re sult suggests that A. fissifrons scavenge an webs of Cyrtophora hosts by co llecting smalt prey ignored by the hosts.