SIZE DEPENDENT INTRAGUILD PREDATION AND CANNIBALISM IN COEXISTING WOLF SPIDERS (ARANEAE, LYCOSIDAE)

Abstract

Two species of wolf spider, Hogna helluo (Walckenaer 1837) and Pardosa milvina Hentz 1844 dominate the predatory community on the soil surface of agroecosystems in eastern North America. Although as adults they are very different in size, differences in phenology ensure that they overlap in size at various times during the year. In a laboratory experiment, we explored the propensity of each species to attack and kill the other wolf spider species (intraguild predation), conspecifics (cannibalism) or crickets (ordinary predation). Both spiders attacked and killed a broader size range of crickets more quickly than they approached other spiders. We found no differences in Hogna foraging on conspecifics or Pardosa, but Pardosa attacked and killed Hogna more readily than conspecifics. Because Hogna was so slow in attacking other spiders, their impact as an intraguild predator may be quite small, especially if their approach to crickets is an indication of their predatory tendencies with insects. On the other hand, Pardosa attacked and killed small Hogna as readily as crickets, which suggests they may have an influence on Hogna populations if Hogna young emerge coincident with large juvenile or adult Pardosa.