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Scientific name: Formicidae

Average size: 1/8 – 1/4 inch

Commonly found: Where food is present

Diet: Omnivorous foragers; Especially attracted to sweet or sticky foods

General characteristics and facts:

  • There are over 270 ant species in California
  • They live in colonies with an average population of 3,000-5,000 ants
  • One ant can lift an average of 20 times it’s body weight

The Argentine Ant:

The most common ant in Northern California that causes problems is the Argentine Ant.

Biology: Though the Argentine Ant is a small, non-stinging ant, it is a very territorial and aggressive ant that will drive away or kill competing ant species. Neighboring colonies of Argentine ants appear not to be aggressive toward each other, allowing for the rapid spread and domination by this species. Colonies contain thousands of workers and many queens, and mating will take place within the confines of the colony. New colonies are often formed by budding off from the parent colony. Nesting is usually in the soil, commonly under concrete slabs, but may also be found in any other convenient void, such as in trees, wall voids, under insulation, or under debris on the soil. Soil nests are generally very shallow. While protein foods are part of their diet, their preferred foods are sugars, including household food products, fruits in gardens, and honeydew.

Identification: This is a single-node species with small workers only about 2.5 mm long, and with all workers the same size. The Argentine can be separated from the similar Odorous House ant by its visible node and by its dull gray-black to gray-brown color. When viewed from the side the Argentine Ant has a distinct dip in the top of the thorax. There is no circle of hairs around the anal opening. The first segment of the antenna is not longer than the head, and the legs are not noticeably long, as compared with the crazy ant.

Characteristics Important in Control: Control of most ants includes correction of the attractions that drew them to a property, including shelter sites, food sources, and moisture conditions. Elimination of insects that provide protein or honeydew sources reduces ant foraging in an area, very important for this species, and cleanup of unnecessary debris or objects on the soil that provide shelter eliminates nesting. Ant bait products in granular, liquid, or gel formulations can be effective, and carbohydrate baits may be preferred. Locating the nest of these ants is critical, and if it is found treatment directly into the nest with a residual dust insecticide can be effective.

The Carpenter Ant:

The next most common ant in Northern California that causes problems is the Carpenter Ant.

Origin: Many species of these ants are native to North America, with several species seemingly the most likely to invade structural wood members. There are many destructive species in the Pacific Northwest states, as well as from Florida to the northeast to the southwest and in Hawaii.

Biology: The usual habitat of a colony of carpenter ants is within wood, often wood buried or partially buried in the soil. They also commonly establish “satellite” colonies that may be in a structure, maintaining contact between the two colonies with the workers who travel to and from over well-defined trails. Generally there is a single queen in the colony but often supplementary queens as well. Colonies typically are around 15,000 workers when mature, but potentially could be over 100,000 workers. Foods are both carbohydrates and protein, with insects a major part of the diet. These are single-node ants without a stinger, although they are capable of biting. As they expand their colony they eject “frass”, which is wood chips and other debris such as leftover insect parts. This frass is often seen in structures before the ants are, as they are primarily nocturnal in habit. Carpenter ants are also typically polymorphic, with various sizes of workers in the colony.

Identification: Worker ants are easily identified to the genus Camponotus by the single, large node and the evenly rounded profile of the top of the thorax. It has no dips or spines on it, but is an even, curved line from front to back. There is a circular fringe of hairs around the anal opening and the antennae have 12 segments. Colors range from tan to black to reddish to orange to black/red combinations. Workers vary from 6 to 13 mm in length.

Eradication and Control: Finding and treating directly into the nest with a residual insecticide will result in effective kill of the ants there, and a dust insecticide may be most effective. Satellite colonies in structures may be treated directly, or with applications into voids the ants travel through. Bait products seem to be accepted readily as well. Reduction of excessive moisture in the structure and removal of unnecessary wood materials outdoors will reduce the attraction of an area.

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