This is the time of year we begin to notice activity by one ofour most common ant species, the larger yellow ant (LYA). LYA isfound throughout Iowa and because of its prevalence next to housesis also called the "foundation ant." Normally, these ants liveoutdoors in old logs and stumps and under stones. During the latesummer and fall, however, entire colonies may move toward buildingsand try to enter through cracks or gaps in the foundation. Swarmsmay be seen either outdoors or inside the house.
A characteristic of migrations by LYA is the mixture ofwingless worker ants and winged reproductives (swarmers) travelingtogether. Both workers and swarmers have a yellow to yellow-browncolor. Workers are slightly less than 1/4 inch long and havedistinctly tiny, black eyes. Swarmers are about 3/8 inch long andhave transparent wings. A useful diagnostic characteristic is thatboth workers and swarmers give off a lemon or citronella odor whencrushed.
Control of larger yellow ants is not critical, since theycause little damage other than the annoyance of their presence. Ants found outdoors can be ignored unless large numbers of coloniespresent an unacceptable risk of invasion. Then the foundation andyard adjacent to the house can be treated with a residualinsecticide such as diazinon, Dursban or malathion.
Colonies that have wandered inside need only be vacuumed orswept up and discarded. If the ants do nest indoors it is usuallysomewhere in the basement under a loose brick or board or in acrack in the wall or floor. The ants do not forage for foodthrough the house and apparently cause very little damage except tocreate piles of dirt at the entrance to the nest. The temporarynests can be sprayed as located, if desired, with a homeowner,household insecticide product such as "ant and roach killer" or"home pest control spray." Reportedly, these ants try to return tothe out-of-doors sometime in the early spring if left undisturbed.
This article originally appeared in the September 16, 1994 issue, p. 137.