DIRECT AND INDIRECT EFFECTS OF GENERALIST PREDATORS ON A TERRESTRIAL ARTHROPOD COMMUNITY

The densities of an assemblage of cursorial spiders and a mantid, Mantis religiosa, were elevated in replicated field enclosures to compare their impact on a terrestrial arthropod community. Mantids reduced overall biomass 88% relative to controls by directly eliminating grasshoppers and crickets, and to a lesser extent by reducing numbers of cursorial spiders. Spiders also eliminated grasshoppers, but indirectly enhanced cricket numbers, a compensatory effect which canceled their effect on total biomass. Numbers of cursorial spiders were lower in enclosures initially containing elevated spider densities than in controls, suggesting that increased predation among these spiders reduced predation on crickets.