Reducing Native Ant Abundance Decreases Predation Rates in Midwestern Grasslands

Diverse and robust predator communities are important for effective prey suppression in natural and managed communities. Ants are ubiquitous components of terrestrial systems but their contributions to natural prey suppression is relatively understudied in temperate regions. Growing evidence suggests that ants can play a significant role in the removal of insect prey within grasslands, but their impact is difficult to separate from that of nonant predators. To test how ants may contribute to prey suppression in grasslands, we used poison baits (with physical exclosures) to selectively reduce the ant population in common garden settings, then tracked ant and nonant ground predator abundance and diversity, and removal of sentinel egg prey for 7 wk. We found that poison baits reduced ant abundance without a significant negative impact on abundance of nonant ground predators, and that a reduction in ant abundance decreased the proportion of sentinel prey eggs removed. Even a modest decrease (~20%) in abundance of several ant species, including the numerically dominant Lasius neoniger Emery (Hymenoptera: Formicidae), significantly reduced sentinel prey removal rates. Our results suggest that ants disproportionately contribute to ground-based predation of arthropod prey in grasslands. Changes in the amount of grasslands on the landscape and its management may have important implications for ant prevalence and natural prey suppression services in agricultural landscapes.

Laboratory Studies on the Feeding Habits of Seven Species of Ants (Hymenoptera: Formicidae) in Ontario

Preliminary laboratory investigations of the feeding habits of seven species of ants occurring in southern Ontario showed that Camponotus herculeanus (Li.), Crematogaster lineolata (Say) and Formica exsectoides Forel are very predacious and will also eat dead insects. Myrmica americana Weber, Solenopsis molesta (Say) and Tapinoma sessile (Say) are also predacious, but probably because of the small size of the individuals and the colonies they are unable to capture large living insects. Lasius neoniger Emery, a relatively timid ant, may develop large populations and consume considerable numbers of other insects, but it is not recommended as a control agent because it can become troublesome on lawns.