Interactions between the invasive Linepithema humile and honeydew-producing Hemiptera

Honeydew producing Hemiptera are important to the survival of the Argentine ant in its introduced range. We investigated the role honeydew-producing Hemiptera had on Argentine ant survival in an infestation in Raleigh, North Carolina. Within this infestation there was a facultative mutualism between the Argentine ant and the endemic terrapin scale on red maples prevalent during the warmer months. We investigated the effects of excluding Argentine ant foragers from the host tree canopy on each participant. We also investigated whether denying access to honeydew-producing Hemiptera would result in an increase in toxicant consumption. During the winter months, we investigated the apparent role loblolly pine plays in providing a winter food source for the Argentine ant.;The Argentine ant entered into a mutualism with the native terrapin scale on the host red maple. This mutualism imposed an indirect cost on the host tree with smaller seeds and leaves on Argentine ant infested red maple. When Argentine ants were excluded from trees, terrapin scale populations collapsed and local Argentine ant nests relocated away from excluded trees. Bait consumption by Argentine ants was lower where access to honeydew-producing Hemiptera was denied. We attribute this to longer distances reducing foraging effort of Argentine ant colonies.;The Argentine ant cannot survive extended periods when temperatures remain below minimum foraging limits but above freezing. Argentine ants aggregated around loblolly pines and we suspect that this aggregation was not to escape cold temperatures but to concentrate around a reliable winter food source. We found the bark temperature on sun-exposed loblolly pines were elevated during the winter months to temperatures suitable for successful Argentine ant foraging. We found that workers trailing down the trunk were heavier than those trailing up the trunk indicating that the Argentine ants are feeding on a liquid food source, probably honeydew.