The Argentine ant, Linepithema humile (Mayer), is a common invader of residential and commercial structures. It is ranked as the number one urban pest in urban areas where it occurs. L. humile makes a shallow nest that is easily flooded and it has been theorized that this flooding forces the ants into structures for refuge. It has also been postulated that L. humile is invading structures in search of water or to avoid high temperatures. We hypothesize that seasonal ant movement is related to food stress and changes in the availability of honeydew producers in the landscape. Ants counted on ten species of trees throughout the year showed ant counts peaked in June for four species while five species peaked in August and September. Three of these species ((Pinus radiata (D. Don), Platanus x acerifolia (Willd.), Ulmus parvifolia (Jacq.)) were selected for comparisons between honeydew production and trailing ants. Results showed that ant counts on U. parvifolia, P. radiata, and Platanus x acerifolia peaked in mid-September. There was a significant positive correlation between ant counts and honeydew production for U. parvifolia and P. radiata, while only a weak positive correlation for Platanus x acerifolia. This study lays the groundwork for testing the hypothesis that Argentine ants are invading houses in response to food stress caused by seasonal changes in tree-dwelling arthropods. It has been previously reported that Argentine ants preferentially feed on carbohydrate or proteins depending on the time of year. Types of baits (protein or carbohydrate) used for ant control and their effectiveness are directly impacted by this seasonal change in feeding preferences. The information gained from this and future studies may help to reduce the levels of insecticides used for Argentine ants within the urban environment.
Species 1: Hymenoptera Formicidae Linepithema humile (Argentine ant)
Keywords: Honeydew, Landscape Trees
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA