Background/Question/Methods Mutualisms have the potential to aid in the success and spread of invasive species.  Several species of invasive ants engage in food-for-protection mutualisms with honeydew-producing hemipterans and plants with extrafloral nectaries.  In the US, the red imported fire ant, Solenopsis invicta, and Argentine ant, Linepithema humile, frequently tend aphids and mealybugs.  However, it is not known how frequently these invasive ants recruit to carbohydrate resources (e.g. honeydew-producing hemipterans and extrafloral nectaries) in their native range.  Release from competition with aggressive arboreal ants from their native range may lead to greater use of carbohydrate resources by S. invicta and L. humile in their invasive range.  We tested the hypothesis that S. invicta and L. humile more frequently tend arboreal carbohydrate resources in their invasive range in the US than in their native range in Argentina.  We placed sugar water baits on the ground and on trees in the US and in Argentina and monitored which species of ants recruited to these baits. 
Results/Conclusions In the US, S. invicta and L. humile dominated sugar baits on the ground and on trees.  These invasive ants were also frequently found at sugar baits on the ground in their native range in Argentina.  However, neither species was frequently found tending sugar baits on trees in Argentina.  Observations of foraging workers of both species in the US and Argentina supported the results of the sugar baiting.  Both S. invicta and L. humile were more frequently found foraging on trees and tending natural Hemipteran associations in their invasive range in the US than in their native range in Argentina.  These data suggest that opportunities to monopolize arboreal sources of carbohydrates might be much greater in introduced populations.  Differences in access to carbohydrates may be due to differences in the competitive environment between the US (where there are few arboreal specialist ants) and Argentina (where there are a number of aggressive arboreal ants).  Future studies will test the mechanisms responsible for greater use of carbohydrate resources by S. invicta and L. humile in the US, the benefits colonies gain from consuming these resources and whether or not this may have aided in their ability to invade and spread.