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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

June 1999

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Know your ants

name description food sources foraging habits nesting habits mating habits control strategies
Black Carpenter Ant (Camponotus pennsylvanicus) Black; thorax and petiole sometimes light to dark brown; workers " to " long; thorax evenly rounded; long, grayish or yellowish hairs on upper surface of body Outdoors: live and dead insects; honeydew; juice of ripe fruits, not wood.

Indoors: meats, grease, and fat; sugar, honey, syrup, jelly, not wood.
Group recruitment, in columns, may make conspicuous trails on lawn or soil.

During warm months may forage indoors, frequently in moist areas and at night
Rotting wood in trees and stumps; may chew out softer areas in sound wood.

In moist or damaged wood of houses, in bathroom, under roofs, in wall and door voids.
Outdoors: swarms in April to June, or warm sunny days in late winter.

Indoors: swarms may be seen during winter months.
Replace damaged or decayed wood and eliminate moisture.

Use physical controls or sprays for exposed nests, dusts for nests in voids.
Field Ants (Formica spp.) Black, red, or combination of colors. Workers 1/8" to " long. Honeydew, nectar, insects and household sweets Deploys large number of ants on trunk trails; not likely to forage indoors; enters homes sporadically and singly. In open soil in fields or woods or under stones, some build large mounds.

Not indoor nesters, but ants nesting under concrete slabs may enter through cracks.
Swarms from July to September.

In some species, supercolonies have many queens and spread by budding.
Look for and treat outdoor nests, treat house perimeter if you don't find the nest.

If ants are nesting under homes, use commercial bait or boric acid plus honey or syrup
Larger Yellow Ants (Acanthomyops interjectus) Yellow to reddish brown; workers 3/16" long.

Ants emit a pleasant, lemony smell when crushed or disturbed
Fosters honeydew-excreting insects on rootsMostly subterranean and nocturnalIn soil under stones or logs in woodlands or meadows.

Can nest under concrete and around foundation walls; does no damage to masonry
Swarms April to August, maybe in winter if nesting under heated concrete slabs.

Nighttime nuptial flight; mating occurs on ground near nest
Difficult and needless to control if nesting under concrete slabs.

Vacuum up large numbers or use insecticides for flying insects.
Pavement Ants (Tetramorium caespitum) Reddish brown to black; workers 1/8" long. Head with furrows, or lines, running top to bottomDead and live insects; honedew, seeds or the plant sap.

Prefers meats and greasy foods indoors; also eats sweets
Ants are known to engage in territorial wars that resemble wrestling matches. In soil under sidewalks, driveways, stones, logs, etc.

May nest under houses with concrete slab foundations and enter homes through cracks.
Swarms May to July. If nesting under heated slab foundation, they may nest in winter. Look for and treat outdoor nests or treat each point of entry on thehouse perimeter.

If they are nesting under a concrete slab, bait with boric acid plus peanut butter or grease.
False Honey Ants (Prenolepis imparis) Light to dark brown; workers 1/8" long Thorax uneven in profile, looks "pinched" Honeydew, aphid tenders; sometimes gnaw the tips of buds and shoots for juices.

May eat sweets indoors
Very cold-tolerant; may forage at temperatures close to freezing. Travels in thin columns Builds inconspicuous nests usually in open, shady sites. Does not nest indoors. Usually swarms in April to May Check for nest in open, shady areas and treat house perimeter.

Commercial baits or boric acid plus honey or syrup will attract ants.
Odorous House Ants (Tapinoma sessile) Soft-bodied; brown to dark reddish brown; workers 1/10" long. They smell like rotten coconut if crushed or disturbed.Honeydew, insects, visits floral nectaries of plants.

Indoors may eat sweets and meats.
Workers are active and rapid; normally travel in files.

May forage indoors if honeydew is in short supply.
Opportunistic nester; often nests under objects lying on the ground. Swarm June to July.

Colonies have many queens; spread by budding.
Can nest in building foundations, under floors, or in wall voids.Check for and treat outdoor nests under stones, firewood, bricks, or treat entry/perimeter.

Commercial baits may be effective or use boric acid plus honey or syrup
Cornfield Ants (Lasius alienus) Light to dark brown; workers 1/10" long Robust, soft-bodied; thorax uneven in profileHoneydew, floral nectar, seeds, live and dead insects.

Invades houses for sweets and meats.
Tends aphids in the nest and transports them to crop plants; may invade homes and tend aphids on infested houseplants. Forms small craters in lawn; nest under stones, sidewalks, in rotting logs; rarely nest in homes. Males and winged females occur in nest from mid-summer to fall. Swarms August or September, especially on sunny afternoons.Check for and treat nests in lawn or nearby areas, or treat perimeter.

Commercial baits or boric acid plus peanut butter and honey may be effective.
Pharaoh Ants (Monomorium pharaonis) Light yellow to red with darker-colored thorax; workers 1/16" long Normal-sized compound eyes in proportion to the headGreasy and fatty foods; dead insects; many types of sweets; may eat toothpaste or soap Forms relatively fixed trails to recover large food patches.

Ants come to food in greater numbers when food is located a second time.
Indoors near dark, warm and moist sits. Nests are difficult to locate – these ants are opportunistic nesters in small spaces: countertops, baseboards, wall voids.Rapid population growth; probably breeds continuously. No mating swarms; mate inside nest; spread by budding.Baits are preferred, but effective ones are only available through pest control companies.

Insecticides and household cleaning products will only cause colonies to bud.
Grease or Thief Ants (Solenopsis molesta) Mostly smooth, shiny, yellow to light brown; workers 1/20" long.

Proportionally small compound eyes; tendency to curl up when dead.
Dead and live insects; larvae of other insects; honeydew; seeds.

Prefers protein and fat as house pest – meat, cheese, peanut butter, etc.
Sophisticated mass recruitment; often have well defined trails.Deep in the ground; in rotting wood; independently or in the nests of other ants. Swarms from July through September; indoors swarms in small spaces; nests are often difficult to find. If ants are foraging into building from outside, treat entry point or perimeter.

If nesting indoors, bait with boric acid, peanut butter, and honey.

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