Lasius americanus (American Cornfield Ant) Care Sheet

This guide was compiled and written by serafine of the 'Ants and Antkeeping' discord server, which can be found here. 

This guide has been posted with the permission of the authors. The original article may be found here. The original guide is for Lasius niger, which is almost identical to Lasius americanus, I have edited it as such. 

Caresheet - Lasius americanus

Lasius americanus can be found all over the northern hemisphere, it is one of the most abundant ants in North America and a really great pet ant species. They have adapted very well to human settlements and are particularly dominant in urban areas, occasionally they invade houses but they rarely ever actually nest inside houses and thus are not considered house ants. They will go to great efforts in their chase for perfect nesting conditions - studies found that some colonies carry their brood up into satellite nests on the roofs of 50 meter high buildings to benefit from the intense warmth up there.

A lot of people think that because these ants are so abundant they'd be boring, but they are not. Lasius americanus is incredibly resilient, active, fast growing, aggressive, recruits very effectively and utterly dominates areas it managed to establish itself in, wiping out other ant colonies that happen to end up inside it's territory with great efficiency.

This species is often confused with L. neoniger, pallitarsis, and crypticus. As a general note, L. americanus is darker, and is more prevalent in humid conditions, and flies much earlier than the other species, which begin their flights in August-September.

 Lasius americanus  was originally described as a subspecies of Lasius niger. Later, it was considered a synonym of Lasius alienus, until 2018 where it was renamed Lasius americanus


-Familia: Formicidae/ants (Latreille, 1809)

--Subfamilia: Formicinae/scale ants (Lepeletier, 1836)

---Tribus: Lasiini (Ashmead, 1905)

----Genus: Lasius (Fabricius, 1804)

-----Subgenus: Lasius s. str. (Fabricius, 1804)

------Species: Lasius americanus (Emery, 1893)

Basic information

Origin: Canada, United States

Habitat: Prefers warm and temperate climate, avoids shady woods and moors. Is well adapted to urban environments and can be found in cities, parks, gardens and acres, sometimes up to more than 100 nests per 100 m².

Colony form: monogynous, highly aggressive towards other ants, very dominant in areas under it's control* There exists a less aggressive, smaller polygynous strain

Colony size: up to 50.000 workers

Colony age: up to 25 years

Founding: claustral, up to 25% in pleometrosis

Workers: monomorph

Nesting sizes: Soil nests of up to 2 meters in depth, under stones, sidewalks, pavement, sometimes also in dead wood. Can build (relatively flat) soil mounds, will build roofs over their main ant trails. Often founds satellite nests near food sources or warm places.

Feeding: Trophobiosis, Zoophagy (liquid sugars und arthropods)

Hibernation: October – March at 5-10°C, stops laying eggs after summer due to an endogenic rhythm, exogenic (temperature-dependent) hibernation, mediterranian and subtropical colonies may have reduced hibernation

Diapause: during dry hot periods the colony will rest within deeper nest chambers

Reproduction: Nuptial flight in June – August, will swarm on humid warm days during afternoon. Stray queens can often be found until it gets dark.

Nuptial flights are locally synchronized which leads to massive amounts of queens being ejected from thousands of nests at the same time. When these ants fly it is literally impossible to miss them, they're everywhere. They seem to be more prevalent in British Columbia than in other parts of Canada, where they face a greater degree of competition from other Lasius.


Workers: shimmering black to dark brown, silver hairs

Queen: shimmering black to dark brown, silver hairs

Males: shimmering black to dark brown, silver hairs


Workers: 3-5mm

Queen: 8-9mm (occasionally up to 12mm), chubby

Males: 3,5-4,5mm, thin, small head with big eyes, almost looks like a small wasp

Development time

at 25°C

Workers: 4-6 weeks (sometimes up to 10 weeks)

Egg - Larva: 9-16 days

Larva - Pupa: 9-13 days

Pupa - Worker: 9-12 days

Notes: -

Antkeeping information

Recommended for beginners: Definitely yes, but keep in mind that colonies grow fast and can quickly become massive in size.

Temperature: Outworld: 18 - 30°C, Nesting area: 20 - 26°C

Humidity: Outworld: 30 - 50%, Nesting area: 50 - 60%

Nest types: Soil nest, sand-clay farm, gypsum, Ytong, acrylics and 3D-printed nests (preferrably with a bottom coat of sand-clay or grout). The ants need moist areas for their brood, these can be provided by a water test tube attached to the nest.

Formicarium size: Should fit the current colony size. Colonies grow fast so be ready to expand their setup.

Formicarium accessories: Optional heat source (heat mate, heating cable or heat lamp), they don't really need it though.

Substrate type: This species can walk well on almost any surface. Glass, vinyl tubing, acrylics, sand, clay and grout pose no issues. They can also climb vertical and upside down on glass.


Lasius americanus workers are extremely curious, frequently scout their territory and immediately explore every new space they discover - even relatively small colonies show a lot of outside activity. This, in combination with their small size, makes them pretty good escape artists. Regular barrier checks are a must, if there is a weakness these ants will find it.

Once they have reached a few hundred ants the colony becomes very efficient at recruiting workers to a food source. They will quickly swarm and occupy everything that seems edible. Unused or rejected food will often be burried with substrate material. They even start to react to vibrations, so if you open the lid of an outworld you can expect a few workers coming out of the nest to look what's all the noise about - this makes them find new food almost instantly.

In the third or forth year (when there are thousands of workers) they will start to seriously tackle your barriers. Regular checks are a must and it is strongly advised to give them some room to walk around (several outworlds connected by a few meters of tubing) - the less room they have the more aggressive and persistent they will try to break free. A large colony needs a large territory to gather enough food - this is a behavioral imprint and no amount of food given will stop them from doing what their programming tells them to do.

! Lasius americanys is extremely aggressive towards other ant species. If you keep other ants make sure that the Lasius not only cannot escape their setup but also that they cannot enter the setups of your other colonies. Lasius americanys will attack and very efficiently kill off other colonies if they get a chance (this includes aggressive species like Pheidole megacephala and Tetramorium ants). 

Additional antkeeping information

Very adaptable species that can thrive in a broad variety of nests and nesting conditions. Does still well even under less-than-ideal conditions.

Doesn't care too much for vibrations and light either. Can get used to daylight but prefers dark nests.

Colonies grow fast, so plan ahead. Under good conditions they can easily grow to over 1000 workers in year 2.

Colonies can grow to quite massive proportions of over 50.000 workers – if you wish for a good beginner species that is equally adaptable but less aggressive and doesn't grow that big take a look at Formica fusca.

Small colonies are quite resourceful with protein food but will drink a lot of sugar water. Larger colonies will ferociously devour any food given.

The workers are REALLY FAST and very aggressive - do NOT try to feed them inside their tube, workers will inevitably escape and get lost.

As soon as they have their first workers put their tube into an outworld and offer food there.

Test tubes of around 15x150mm are great starter nests. These tubes feature a large enough water tank for several months which means you won't have to move your ants before the colony grew to a good size. The entrance area should be sized down with cotton and a large straw (as passage) to reduce evaporation.

! Some Lasius americanus colonies develop a habit of sticking small debris into the gaps between the nest/outworld frame and the lid. This should be prohibited if in any way possible as over time it can build up enough pressure to lift or even snap off the lid.

Diet & Nutrition


Sugar water, honey, maple syrup and similar sugary liquids all work well. I've even seen them drinking spilled milk on a sidewalk once.

Be careful when diluting honey to honey water, during hot weather honey water can ferment within a day and if you use a gravity-assisted feeder the evaporating gases might even press the honey water out of the feeder.


Fruit flies, flies and small spiders are perfect food for small colonies.

Larger colonies will eat crickets, all sorts of flies (terflies, meat flies, green bottle flies) and mosquitoes, grasshoppers, insect pupae (bee pupae, meat fly pupae), spiders, mealworms, superworms, roaches and even stuff like wet cat food or chicken meat.

It is recommended to give them a small amount salt water or some salty food (like ham) occasionally.

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