Argentina antThe Argentine ant (Iridomyrmex humilis Mayr.) is a native of South America which probably reached this country between 1880 and 1890 at New Orleans and now is present nearly everywhere in the United States south of Virginia, Kentucky and Missouri and is also in California as far north as San Francisco.
The adults (Fig. 1) are brown in color. The queens are about a quarter of an inch long, the males about half that length and the workers about a tenth of an inch long. Their summer nests may be located anywhere - under sidewalks, under the sills of houses, in brick piles, stone piles, under a piece of board or a piece of tin, in an old tin can - in fact, in any place convenient to the food supply.
In the winter months there is a tendency to concentrate into larger colonies, and they seek warm, dry, secure nesting places in which to hibernate. Egg production is probably quite large - perhaps 50 or more per day under favorable conditions - and an average of 40 days in warm weather is required for development from the laying of an egg to the emergence of the adult worker.
This is one of the worst of house pests known in the regions where it is abundant. lts small size enables it to enter through the smallest cracks and it goes everywhere in houses after its food. It will eat practically everything in the way of foods, both raw and cooked, and no part of a house is free from its presence. The cold of ice chests does not repel them and beds are not entirely protected by placing the bedposts in dishes of water, as after a few hours a film of dust forms on the surface of this, over which with their light bodies they are sometimes able to pass. Though they do not sting, they bite freely and are able to cause some pain in this way. People asleep have been found with ants in the nose, ears and mouth. They visit aphids, soft scales and other insects for honeydew and, to some extent at least, their presence is favorable to these pests and makes their control more difficult.