Small Ants
(Click here for information about Carpenter Ants.)There are thousands of species of small ants. Most are harmless, and some are even quite beneficial. Many ants are scavengers who help dispose of dead and decaying plants and animals, while others prey on harmful pests. Some small ants, however, are pests and need to be controlled — at least when they are in or near our homes, businesses, and recreational areas. Ants can contaminate food with their by-products or when they transmit filth that they pick up on their bodies. Some can also impart foul odors and tastes by their bodily secretions.
A Small Sampling of Small Ants
Pavement ants are one of the most common small ants that homeowners come across. They're small (about 1/8" in length ), are black or dark brown in color, and have parallel grooves on the head and thorax. These grooves resemble the pavement markings on a highway; and some exterminators say this is why they are called pavement ants." (Of course, most people say it's because pavement ants are commonly seen walking on the pavement.) Pavement ants will eat pretty much anything, but they prefer sugary foods, proteins, and fats.
Argentine Ants are sugar-feeding ants who feed on things like candy, sugary syrups, honeydew, nectar, and so forth. They live in very large colonies, which can make control very challenging. Argentine ants usually nest outside in protected places such as under rocks, firewood, mulch, and concrete slabs. They often move indoors when the weather gets cold.
Odorous House Ants are give off an unpleasant odor, especially when they are crushed. They're primarily sugar feeders and prefer sugary foods such as pancake syrup, honeydew, fruit juices, and nectar. Odorous house are more often seen indoors during cooler weather, when they can't find their natural sources of food outdoors. 
Pharaoh Ants are very tiny ants, only about 1/16 of an inch in length, on average. They're omnivores and will eat pretty much anything, and they commonly forage over very great distances (at least, in ant terms) looking for food.
Pharaoh ants are very difficult to control. Repellent products like sprays and dusts tend only to "fracture" the colony into multiple, smaller colonies. Treatment of Pharaoh ants is definitely a job for a professional exterminator.
Citronella Ants range from about 1/8" to 3/8" in length, on average, and are yellow or orange in color. They emit a citronella-like scent, especially when the ants are crushed. (In fact, exterminators often crush these ants between their fingers to identify them.) They tend to live in protected places such as under rocks and slabs, emerging once or twice a year in massive swarms that often lead panicked homeowners to believe that they have termites.