Ants are very successful social insects. They have small to very large colonies that contain workers (which are sterile females), queens (one or many), secondary reproductives that take the place of a queen that passes on and winged reproductives (known entomologically as alates) whose sole responsibility is to start new colonies. Many of our most troublesome pest ant species are transplants from some other part of the world. There are approximately 245 species of ants in California and about 25 of those species are introduced from other areas. Nine species are considered household pests, but one species is the dominant ant pest in California which is the Argentine ant.
Argentine ants (Linepithema humile)
Argentine ants are small, monomorphic (all workers the same size) and brown in color. They are one of the most successful ants species on the planet. They have huge colonies and when they move into an urban area, they displace any native ant species. Unlike other ants who fight when they encounter other colonies of their same species, Argentine ants will merge and form super-colonies, and in some cases, mega-colonies. There is one mega-colony of Argentine ants in Europe that extends over 3,700 miles and encompasses parts of Spain, Portugal, France and Italy. This mega-colony is estimated to contain hundreds of billions of ants. They came to the United States in 1891, landing in New Orleans. Since then they have spread to several other states. They were first found in California in 1905 near Ontario. Three years later they were found in Alameda, East Oakland, San Francisco, San Jose, Los Angeles, Azusa and Upland. The Argentine ant is now found in almost all urban areas of California where it is a major household pest. Besides California and Louisiana, there are records of these ants in Utah, New Mexico, South Dakota, Arkansas, Illinois, Florida, Alabama and Hawaii.
They originally came from Brazil, moved to Argentina and now they are all over most of California and some other parts of the country as well. They have many queens in a colony and each one is capable of producing 60 eggs per day.
Nests are often found in urban habitats and it does not live in arid areas. They are very persistent house pests. Outside it will nest in exposed soil and under stones as well as in rotten wood, refuse piles, bird nests, bee hives and in dead trees. They do not swarm as many other ants do, but the winged reproductives mate in the nest. Outside they will feed on a variety of foods, including certain plants, buds of fruit trees and even ripened fruit such as figs. They also feed on the honeydew secretions of aphids, scales and mealybugs. In a home they will eat almost anything edible, including sweets, meats, pastries, fruit, dairy products, eggs, animal fats and vegetable oils. They are particularly fond of sweets. They will crawl over everything in a house, including appliances, furniture, shelves and clothing. The good news is that they do not sting. However they can bite.
Pharaoh ants (Monomorium pharaonis)
Pharaoh ants are very small, yellowish ants that are monomorphic. They got their name because they were originally discovered and described in Egypt in 1758. They are found in many areas of the United States. They are especially common in hotels, apartment complexes, groceries and hosptials.
They will nest in any small, dark voids such as old boxes, empty bags, stacked newspapers and even an unused salt shaker. Outdoors they will nest under objects on the ground, in potted plants, in stacked firewood or piles of bricks. They are primarily nocturnal and mainly come out to feed at night.They have very large colonies, often exceeding a quarter of a million ants and many queens. They do not swarm to reproduce as most ants do, but use a system called “budding.??? This is where reproductives just crawl off and mate nearby. Colonies of pharaoh ants usually contain many nests and it is essential to control all of them or you will never get rid of them. Pharaoh ants are a major pest in hospitals where they have been associated with over 20 disease causing pathogenic organisms and they often enter isolation wards, operating rooms and patient rooms where they feed on blood and blood products and then contaminate sterile areas.
Other household ants found in Californa include pavement ants (Tetramorium caespitum), odorous house ants (Tapinoma sessile), thief ants (Solenopsis molesta), velvety tree ants (Liometopum apiculatum) and carpenter ants (Camponotus spp.). Carpenter ants can cause damage in a home.
It is very important to get any ants you have that are a pest properly identified.