Several authors pointed out that different spider species select different scaffolds. For example, ENDERS (1974) stated that two species of the genus
Argiope coexist by selecting different scaffolds.
But the kind and the quantity of preys caught by each spider species have not been investigated at the place where several species coexist.
So the author analyzed the ecological distribution of each species in relation to prey distribution and the condition of scaffolds; then he investigated the quantity of preys caught by each species at various sites selected by spiders, and analyzed the conditions of coexistence of several species.
Four spider species investigated inhabit sympatrically at stream side.
Meta kompirensis and
Tetragnatha spp. (
T. praedonia and
T. japonica) weave only at the space above the stream, but
Leucauge agnifica weaves both at the space above the stream and among plants on the bank.
Meta makes the largest web and
Leucauge makes the smallest one, so
Meta weaves mainly at the place with lower coverage and
Leucauge with higher coverage, but
Tetragnatha weaves both at places of lower and higher coverage.
Prey insects are caught mainly by the webs above the stream, especially at the place where
Meta and
Tetragnatha weave frequently. It seems that
Tetragnatha concentrates on such a place because of prey abundance, for this species abandons unproductive webs and weaves at another place. The concentration of
Meta is not due to prey abundance, but due to the good condition for weaving.
Leucauge can not weave at such a place because it's small web can not be made there owing to poor scaffolds.
The interferences among spiders change the web distribution of each species also. Inter ferences shorten the web-keeping time of each species, especially of subordinate species (
Leucauge and
Tetragnatha) and subordinate individuals (smaller individuals). But many insects are caught at places where interferences occur frequently, so the number of insects caught by spiders is larger there than at the place where interferences occur rarely. Therefore subordinate species (or individuals) can coexist with dominant species (or individuals) if the latter does not keep the resource exclusively at the place where prey insects are abundant.
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