Argentine ants (Iridmnyrmex hum ilis) are the, world's worst ant pest, being more persistent than any other species. They are practically omnivorous in their feeding habits, but may prefer sweet things. They may he found throughout the house, even in refrigerators and beds, but particularly in pantries, kitchens and dining rooms. The serious nervous irritation and annoyance caused by their persistent infestation are harmful to human health, as can be their unhygienic habit of invading garbage tins and rubbish heaps.

They are important orchard and garden pests because they protect sap-sucking insects (such as aphids, scales and mealy bugs) from their natural enemies and also damage flowers when in search of nectar.

Hens may be driven from nests, especially when hatching begins or if an egg is broken in the nest. Newly-hatched chickens may be killed by the ants, and caged birds may also be attacked.

Like those of other ants, Argentine ant colonies contain queens, males and workers, and brood consisting of eggs, larvae and pupae. Workers arc the most commonly seen and cause the actual damage and annoyance: but, at times, queens will travel in the well-defined trails, probably to a new nest site. When crushed, they do not give ofr the formic acid smell so characteristic of other ants, but may have a musty or greasy odour. They cannot sling, but may bite if their movement is restricted.

Eggs hatch in from 12 days to nearly two months. The larval stage occupies 11 to 60 days, and the pupal period from 10
to 25 days. The minimum period from egg to adult is about one month, but it may take four to live months.

Nests, usually near food sources but seldom inside or under buildings, are found in lawns, alongside paths, gutters and kerhings, under garbage cans, pieces of iron, rubble, waste cloth or paper, in damaged fences and street poles, brickwork of houses, compost heaps, raised areas of soil in low-lying land and sandhills. They are generally shallow, often no more than I-inch from the surface. They rarely tolerate other ant species;, which makes it comparatively easy to delimit an infested area, and their natural- Spread is fairly slow. They cannot found a colony unless at least one fertile queen is present. Transport, even in large numbers, of workers only is not sufficient to found a colony in a new district. .