Ants in the Home Fact Sheet No. 5.518 Insect Series|Home and Garden by W.S. Cranshaw* Almost anywhere in the state one the nest, tend the young and do other Quick Facts travels, ants will be the most common necessary colony duties. Many kinds of insects that can be found in yards, gardens, ants produce workers that are all the • Most ants that are found in fields and forests. Tremendous numbers same size (monomorphic); some, such as homes nest outdoors and of ants normally reside in a typical house field ants, have workers that vary in size enter homes only to search lot, although most lead unobserved lives (polymorphic). for food or water. underground or otherwise out of sight. Each colony contains one or, sometimes, Often it is only when they occur indoors or a few queens (Figure 1). These are fertile • Almost all ants are workers, produce their periodic mating swarms that females that are larger than workers and wingless females that search they come to human attention. dedicated to egg production. The minute for food and maintain the Overall, the activities of ants are quite eggs are taken from the queen and tended colony. beneficial. Many feed on other insects, by the workers. Upon egg hatch, the • A small proportion of an including pest insects. Ant scavenging pale-colored, legless larvae are fed and helps to recycle organic matter and their protected by the workers. When full-grown, ant colony are winged tunneling is useful in aerating and mixing ant larvae produce a smooth silken cocoon reproductive forms. These soils. On the other hand, ants sometimes within which they pupate, ultimately emerge periodically in promote the activities of certain plant pests, emerging as an adult ant. Ant pupae are swarms and fly away on notably aphids, that excrete sweet sugary often seen when turning over a rock that mating flights. honeydew that is favored by many ants. exposes a colony and are sometimes • Removing sources of Ants most prominently become mistakenly called “ant eggs”. problems when they are found in homes. As colonies mature, winged forms of food and water will reduce Most ants found indoors in Colorado are ants are also produced. These include visitation of ants and help to merely foragers, seeking food or water in a females that are potential queens and more effectively use baits for home but returning to colonies they have slightly smaller males. These reproductives ant control. established outdoors. A small number of periodically leave the colony during • Slow-acting insecticides in the ants found indoors may become more swarming events, when they fly away en baits allow them to be taken permanent residents and establish a nest masse and attempt to mate. Such swarms within a building. This ability to nest indoors usually occur during a sunny, calm period a back to colonies and are most is most often associated with pharoah few days following a heavy rainfall. effective for eliminating ants. ants; some colonies of pavement ants The swarms of winged ants being and carpenter ants may establish within a pushed out of the colony often attract building. attention and alarm, particularly when they emerge in a garage or other building. However, these ants never return to the Life History and Habits colony after they have left on a mating Ants are social insects that live in a flight. After they disperse, time the ants colony, usually consisting of thousands to mate and the now fertilized females tens of thousands of individuals. Within attempt to establish a new colony. The the colony are various ant “castes” of males die within a couple of days of leaving different forms and function. Colonies the colony following the swarming event. are overwhelmingly comprised of Winged ants are sometimes mistaken workers, wingless females that forage for winged termites. However, ants can be © Colorado State University for food, construct, maintain and defend easily distinguished by having a narrow Extension. 11/96. Revised 1/17. constriction between the thorax and extension.colostate.edu abdomen (“wasp waist”), antennae that are *Colorado State University Extension entomologist elbowed, and hindwings that are smaller and professor, bioagricultural sciences and pest than the forewings (Figures 5). management. 1/2017 insecticides. Other types of ants, such Carpenter ants (Camponotus species) as carpenter ants, may form “satellite are the largest ants that occur in Colorado colonies” that contain large numbers (1/4-3/8 inch) and are particularly of foraging workers but lack a queen or abundant in forested areas. They may developing young. be either black or black with a reddish Worker ants forage constantly during brown thorax. They are most similar to the warmer months of the year. The the field ants but can be distinguished workers lay down chemical trails as they by examining them in side view, with forage that helps direct other workers the thorax of the carpenter ants being to sources of food or water. Feeding uniformly rounded without indentation. habits of the various kinds of ants vary Carpenter ants nest in wood, almost Figure 1: Ant pupae with cocoons, Tending workers. with sugary materials preferred by most always establishing colonies in wood species, at least for part of their diet. that has been softened by decay. Others may favor greasy materials, seeds, Carpenter ants found in homes almost or protein-rich foods such as living or always are foragers that will return to an dead insects. Feeding habits may shift outdoor nest in the yard. Rarely they will during the season with changes in colony establish a nest in the building, always at needs. some point of previous water-damage. Carpenter ants (Figure 5) mostly feed on a mixture of dead insects and honeydew. Ants Commonly Found in Cornfield ants (Lasius species) are Colorado Homes relatively small ants (less than 1/8 Pavement ants (Tetramorium inch) that are usually light to medium- brown colored. They nest outdoors but Figure 2: Pavement ants visiting mint apple jelly. caespitum) are ants to have first found their way to Colorado only in the past sometimes will enter buildings to feed on few decades but now are often the most sweet materials. common species that people notice Odorous house ants (Tapinoma (Figure 2). They characteristically produce sessile) are small (1/10-inch) black ants small mounds of soil at entrances of their that have only recently been found in nest, and nests are often located under Colorado (Figure 6). When disturbed, pavement or rocks (Figure 3). They are they will raise their abdomen and emit an small ants (1/10-1/16-inch), dark-brown odor reminiscent of coconut. They do not colored and have fine grooves that line nest indoors but may enter to forage on their head. Pavement ants forage a wide various foods including sweets, cooked variety of foods, usually consistently vegetables, fruit slices and pastries. Heavy preferring greasy materials. Feeding mulch adjacent to building foundations Figure 3: Soil piled at nest entrance, typical of habits shift during the season with higher has been associated with increased pavement ant. protein materials being sought when problems with odorous house ants. young are being reared and sugars more Pharoah ants (Monomorium Most new ant colonies are developed favored at other times. pharoaensis) are minute (1/12 inch), light- by a queen following a mating flight. Field ants (Formica species) are among brown ants that are adapted to nesting After being fertilized, she moves under a the most common ants found in yards in buildings. Nests can spread extensively rock or some other crevice and sheds her and gardens and are observed in homes through a structure as pharoah ants may wings. She then attempts to establish a most commonly in spring (Figure 4). They frequently move nest locations, produce new colony, largely living off the energy are black or reddish-brown and black multiple queens, and may split to form of her now unneeded flight muscles. ants of medium size (3/16-1/3 inch) and “satellite” colonies. Pharoah ants feed Only a tiny fraction of the females are sometimes are mistaken for carpenter on a wide range of foods that include successful in their efforts and most perish ants. The nest outdoors in loose soil and syrups, jellies, grease, cake, and pet foods. without a new colony developing. If they some produce mounds that incorporate They can be serious pests of hospitals, are successful, the colonies will slowly twigs, dried leaves and other plant dormitories and apartments. grow, becoming full sized after several materials. Migrations into homes occur years. in spring when soils warm enough to Some kinds of ants can establish cause colonies to resume activity but cool Management of new colonies by producing multiple temperatures prevent normal foraging in Household Ants queens within a colony and then dividing yards. Field ants feed on a variety of foods The first and most important step to (“budding”). This habit is particularly but most often are observed visiting reducing problems with ants occurring in common with pharoah ants that may sweet honeydew excreted by aphids and homes is to eliminate sources of food and split colonies and scatter in response or other sweet materials. water that are attractive. In addition to to disturbances, including use of some obvious sources of food left on counters, sinks or floors, spilled food in cupboards often kill only surface foragers, again and food associated with trash baskets providing only temporary control. The may also be visited by foraging ants. great majority of the ants within the nest Dripping faucets and leaking pipes may will not be affected unless insecticides also be important water sources that ants thoroughly penetrate into the colony, will use. Also, if ants have been foraging which may extend a few feet deep. in a home, wash down counters or floors Where entrance areas are disturbed by with some household cleaner to eliminate insecticides or other activities, colonies the odor trails the ants have established will often abandon the treated area and to locate sources of food or water. establish new entrances at a different Most ants found in homes nest location. outdoors, sometimes adjacent to building Alternatives to insecticides are Figure 4: Field ants (Formica species) foundations. Heavy mulch, piled leaves sometimes sought. Boiling water can kill or ground covers that abut buildings small colonies that do not extend too can provide cover for ant colonies and deeply. Large colonies spread over a wide can increase the likelihood of their area, those that extend deeply into the subsequent occurrence in a house. ground, and those that are in sites that Keeping the area around the building would be damaged by hot water (e.g., foundation free of cover can reduce the around plant roots) can not be managed likelihood of ants foraging indoors. by this method. Furthermore, the hazards Insecticides can be useful to control of handling boiling water generally ants and a wide range of ant control exceed that of using currently available products are available. These are primarily ant insecticides, with less likelihood of Figure 5: Winged adult male (top) and queen used either to: 1) generally suppress ant success. (bottom) of a carpenter ant. numbers in a yard; 2) establish perimeter Perimeter Treatments of Buildings. barriers around a home; 3) spot treat Most ants that occur within homes foraging ants found in homes; or 4) originate from outdoor colonies. An incorporate into baits to kill colonies. insecticide barrier maintained around General Suppression of Ants in Yards. the building perimeter can inhibit much Products used for general ant suppression of this activity. Such treatments are include various sprays, dusts or granules generally applied as sprays or dusts to the applied to lawns (Table 1). These surface- soil immediately adjacent to the building applied treatments can temporarily and/or the lower areas of walls. Particular reduce numbers of ants foraging through attention should be given to areas where lawns and on garden beds. However, such ants are known to be able to enter treatments do not penetrate into colonies buildings, such as near foundation cracks nor do they affect ants that use below or windows. However, such treatments Figure 6: Odorous house ants. Photo courtesy ground tunnels for much of their travel. will not be able to well control ants that of Susan Ellis. Similarly, applications of such enter homes through below ground insecticides made directly to nests will openings in building foundations. used by foraging ants to enter living Essentially, all such perimeter areas. However, these have very limited Table 1. Insecticides Used for Control of treatments involve insecticides of and short-term effectiveness as the Ants (listed by active ingredients) the pyrethroid class (beta-cyfluthrin, insecticides degrade and/or the ants Insecticides Used as Sprays, Dusts or bifenthrin, deltamethrin, lambda- change routes of activity. Far more Granules for General Ant Control and cyhalothrin, permethrin) and these Barrier Treatments effective are insecticides used as baits, typically may persist to control ants for fed on by ants and returned to the nest. beta-cyfluthrin bifenthrin a week to around month under outdoor Contact sprays should not be used in the carbaryl deltamethrin conditions. One perimeter treatment vicinity where baits are applied. lambda-cyhalothrin permethrin with a different mode of action is Baiting. Use of ant baits will usually hydramethylnon, an insect growth Insecticides Used as Baits provide the most satisfactory control. regulator. Sold in a granule formulation abamectin/ This strategy involves use of acceptable avermectins under the Amdro trade name, it acts as food into which a small amount of an a bait that may be accepted by some boric acid/Orthoboric dinotefuran insecticide is incorporated. The ants acid/Borax species of ants that occur in Colorado feed on the bait and return it to the homes. Baits are discussed below. fipronil hydramethylnon colony where it is shared with nest mates Household spot sprays. Some indoxacarb (trophyllaxis). household insecticides allow use indoors The types of insecticides used for as a surface spray to kill ants that move baiting ants (Table 1) are very different across treated surfaces. Such treatments than those used as sprays around are best applied to cracks and crevices with some preferring sweet materials (e.g., field ants, cornfield ants), others favoring greasy materials (e.g., pavement ants). Another important factor in bait acceptance is moisture content. Baits often become unattractive when they dry out, a common problem in the arid climate of Colorado. For this reason, liquid and gel formulated baits may often be Figure 7: Insecticide applied as a gel bait. more readily accepted by ants. Carpenter ants are one group of ants that will not visit most solid ant baits but will feed at building perimeters or in spot treatments. some liquid or gel sugar-based baits. Instead of being fast acting, these have Effectively using baits also requires slower effects that allow the forager ant a few steps be taken so that the ants time to carry the treated food back to will visit and feed upon the baits. Most the nest. Boric acid, borax and arsenic important is to deny them alternate food trioxide are some of the older insecticides and water sources within the home. used as baits. Others act as insect growth Thoroughly clean-up food preparation regulators (e.g., hydramethylnon), areas and other sites of ant activity. affecting insect hormones that affect Secure garbage cans to prevent ant growth or prevent queens from foraging. Leaking faucets and other producing fertile eggs. In recent years, areas providing free water should also be several new insecticides have been corrected. marketed that have different activity Spot sprays of insecticides should not allowing highly effective disruption be used in the vicinity of a bait station. of ant colony functions (e.g., fipronil, The point of effective ant baiting is to dinotefuran, indoxacarb). get ants to actively visit the bait. Place The formulation of insecticides used as the baits in areas where ant activity has ant baits is also different. Historically, baits been observed. Ant baits will need to be involved solid food mixtures placed inside reapplied if they dry out or are consumed. a bait station (“ant trap”) that was visited Effects of ant baiting usually start to by ants. In recent years, food baits that become apparent within a week or two are applied as gel droplets or are in bait after they are begun. Under optimum stations that provide liquids have been conditions the ant colony may ultimately marketed. Solid food-based baits are also be eliminated by a bait program. available now in a broadcast form for use Homemade ant baits are sometimes outside. prepared. These involve incorporating a Several features determine if ants small percentage (ca 5-10% by weight) of can be successfully controlled with baits boric acid or borax with some acceptable (Table 2). Perhaps most important is food. Since feeding preferences of ants that the bait is acceptable to the ant so vary, test several foods to see if they are that they will feed on it. Feeding habits visited. Among the commonly available of the various ants found in homes vary foods accepted by ants are either sweet materials, such as honey or apple jelly, Table 2. Steps to take for effectively using and/or greasy, protein rich materials, ant baits such as peanut butter. If these baits are Clean up areas of the home to deny ants made, they must be applied in a manner alternate sources of food. so that pets or children can not reach Fix water leaks and other sources of them. Placement of the bait in a sealed moisture. container with punched entry holes can Avoid using other insecticides that might produce a more protected bait station. deter ants visiting the baits. Baits containing boric acid/borax also Choose an ant bait that is acceptable to the cannot be applied directly to soils where type of ant found in your home. plants are growing as boron-containing Place the bait in an area that is visited by materials can be soil sterilants. ants. Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. Replace ant baits if they dry out or are CSU Extension programs are available to all without consumed. discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.