Ecological trap theory suggests that greater predator activity occurs along edge habitat, thereby reducing prey abundance. Alternatively, environmental gradients associated with edge habitat may be responsible for changes in prey abundance irrespective of predator spatial distribution. To test these alternative hypotheses, I measured the distance soil arthropods were to edge of boxes (21 × 9.5 cm) placed on the forest floor of prairie (precipitation-limited; 1977–1999) and boreal forest (moderate precipitation; 2000–2001) sites. Predator theory predicted that in either environment predatory groups would be located close to edge and herbivore/detritivore groups would not be distributed different from random. In support of this hypothesis, in the precipitation-limited environment 7 of 11 soil arthropod groups were distributed as predicted; however, only 7 of 13 groups followed predator predictions in the moderate-precipitation environment. In support of the environmental gradient hypothesis, 22 of 24 soil arthropod groups were distributed as predicted. Here, all hard-bodied groups, with the exception of snails, were located closer to edge than expected and all soft-bodied groups, with the exception of slugs, were not located closer to edge than expected indicating possible avoidance of external dryness. Tests of these two hypotheses were confirmed with similar results using a regression method to determine if distribution declined from edge to interior. In conclusion, the results did not support the predation hypothesis and instead supported the environmental gradient hypothesis with moisture the likely explanation for the distribution pattern of soil arthropods.