Interspecific Competition Between Spiders and Its Relevance to Biological Control by General Predators

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Abstract
Interspecific competition between two orb-weaving spiders, Metepeira grinnelli (Coolidge) and Cyclosa turbinata (Walckenaer), was investigated by selective removal of the predators. The estimated predation rate of small prey was higher where Cyclosa was alone than where both species were present, because when Metepeira was removed the density of Cyclosa became higher than the combined density of Metepeira and Cyclosa where both species were present and because the consumption rate of small prey by Metepeira was very low compared with that of Cyclosa. The study suggests that, in some circumstances, a subset of predator species could be more effective in reducing prey populations than the entire natural guild.