Ants in the Home Fact Sheet No

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.

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