Found across most of the world, Argentine ants are dull brown and are all about ⅛" (3 mm) long, with a pointed node. They move rapidly in tight trails, prefer sugar but will eat protein and fat, and have a musty odor when crushed. Colonies are typically in damp areas outdoors, but are also found indoors. Eradication is extremely difficult due to multiple cooperating colonies and multiple queens per colony. These ants are black, dark brown, or dark red, or a combination of these. They vary in size from ¼" to ½" (6 to 12 mm), and have one erect node and no thorax spines. They move in loose trails and are often found near wood, along with a strong odor and piles of sawdust, soil, and insect parts. Look for trails across lawns where vegetation has been thinned or removed. Crazy ants are named after their rapid changes of direction, and perhaps for their odd-looking, extra-long antenna and legs. Their slender, dark grey, black, or brown bodies are 1/16 to 1/8" (2–3.5 mm) long, have a flat node that's difficult to see, and have no spines. In the tropics, some crazy ant species are yellowish-brown instead and can be up to 1/5" (5 mm) long, with a darker gaster (rear abdomen). These one-node species are common pests in some areas, but much more limited in global distribution than the species above:  Ghost ants: Very small (1/16" or 2 mm), with a black/brown head and pale abdomen. Flat, hidden node, no spines. Usually outdoors in tropics, or on plants from greenhouses or tropics.  Odorous house ants: 1/8" (3.5 mm) long, one flat, hidden node, no spines. Strong, unusual odor when crushed. Primarily found in trails looking for sugar, but this varies.  Rover ants: male workers are 1/16" (2 mm), small and black with unusual straight antenna. Most easily distinguished by the much larger, winged females, which are found near light or floating in standing water.  White-footed ants: These 1/8" (3.5 mm) ants are usually black with pale "feet." A flat, hidden node, no thorax spines.

Summary:
Identify Argentine ants. Distinguish Carpenter ants. Determine Crazy ants. Identify other species.