Lasius brevicornis (The Short-horned Yellow Ant)

Lasius brevicornis is a captivating and often overlooked member of the "yellow ant" group, a clade of ants within the genus Lasius that have largely abandoned the surface world in favor of a life lived entirely beneath the soil. While its European relative Lasius flavus is the most famous representative of this lifestyle, Lasius brevicornis is a quintessential North American species that exemplifies the specialized adaptations required for subterranean existence. For the ant keeper, Lasius brevicornis represents a unique challenge and opportunity: the chance to observe a hidden world of "root-ranching" and chemical communication that occurs right beneath our feet in meadows, prairies, and open woodlands.

Natural History and Identification

As part of the subgenus Cautolasius, Lasius brevicornis is characterized by its distinct yellow to orange coloration and its diminutive size. The workers typically range from 2.5mm to 3.5mm in length. Unlike the dark-colored Lasius alienus, these ants lack heavy pigmentation because they are rarely exposed to the ultraviolet rays of the sun. Their eyes are significantly smaller than those of surface-foraging ants, reflecting their reliance on touch and chemical signals rather than vision.

The name "brevicornis" refers to its "short horns" or antennae, which are slightly shorter relative to their body size than some of their close relatives. The queens are a beautiful golden-brown or amber color, measuring around 7mm to 8mm. They are much bulkier than the workers, possessing the large fat reserves necessary for claustral colony founding. Identifying Lasius brevicornis in the field can be difficult for the amateur, as they look remarkably similar to Lasius nearcticus; however, brevicornis tends to prefer drier, more open habitats such as upland prairies and meadows, whereas nearcticus is more common in moist forest leaf litter.

Distribution and Native Habitat

Lasius brevicornis is widely distributed across North America, from the Atlantic coast to the Rocky Mountains, and from southern Canada down into the mid-latitudes of the United States. They are particularly abundant in the Great Plains and the Midwest, where the deep, rich soils of the prairies provide the perfect medium for their extensive tunnel systems. They are also found in suburban lawns, where they often go unnoticed until their nuptial flights reveal their presence.

Their nests are exclusively subterranean. They do not build conspicuous mounds; instead, they utilize the root systems of grasses and herbaceous plants as the framework for their colonies. The chambers are often situated directly against the roots of these plants to facilitate their primary means of survival: the farming of aphids.

Diet and Foraging Behavior

Lasius brevicornis is a true "rancher" of the ant world. They are rarely seen foraging on the surface because they derive the vast majority of their nutrition from root-feeding aphids and mealybugs (Coccidae). These ants have developed a sophisticated mutualistic relationship with these insects. The ants protect the aphids from predators and parasites, and sometimes even move the aphids to different roots to ensure they have fresh sap to feed on. In exchange, the aphids provide the ants with honeydew, a sugar-rich liquid that serves as the colony's primary energy source.

In addition to honeydew, Lasius brevicornis workers scavenge for protein within the soil, feeding on small soil-dwelling invertebrates, insect eggs, or dead organic matter. In a captive environment, they can be a bit more "shy" about feeding than surface-dwelling species. They prefer to take their food in the dark and will often cover liquid sugar sources with sand or substrate to create a secure tunnel to the food. Ant keepers must be patient with their feeding, providing small amounts of honey-water and soft-bodied insects like fruit flies or small cricket legs.

Colony Lifecycle and Social Structure

The lifecycle of Lasius brevicornis is centered around the late summer nuptial flights, which typically occur in August or September. These flights are often massive, occurring simultaneously across a wide region after a soaking rain. The winged queens and males (alates) emerge from the ground in the late afternoon, creating a golden haze as they take flight. Once mated, the queens are extremely effective at finding small crevices in the soil to begin their new colonies.

Lasius brevicornis is strictly monogynous, meaning a mature colony will only have one queen. However, like many other Lasius species, multiple queens may occasionally group together to start a nest (pleometrosis), only to have the workers eventually eliminate all but one queen as the first brood matures. The colonies can grow to several thousand workers, but because of their subterranean nature, they remain much more compact and "crowded" in their nesting habits than species that forage on the surface.

Ant Keeping: Care and Housing

Keeping Lasius brevicornis is a study in patience. Because they are subterranean, they are highly sensitive to light and vibrations. A successful keeper must provide a dark, quiet environment for the colony to thrive. Using red-tinted film or simply keeping the nest covered is essential. They are also very sensitive to dehydration; the nest must be kept consistently moist, as these ants lack the thick cuticle of desert-dwelling species and can desiccate rapidly if the environment becomes too dry.

Hibernation is a non-negotiable requirement for Lasius brevicornis. In the wild, they retreat deep below the frost line for several months. In captivity, a 3-4 month period at temperatures between 4°C and 8°C (39°F - 46°F) is necessary to reset the queen's biological clock and ensure healthy brood development in the spring. During hibernation, the ants will cluster together in a tight ball around the queen to conserve moisture and energy.

Recommended Setup

For a subterranean specialist like Lasius brevicornis, the choice of formicarium is critical. They do not like large, open spaces. For founding queens, a simple test tube setup with a generous water reservoir is best. For established colonies, the All-in-One kit is an excellent choice, as it allows for the maintenance of high humidity levels while providing a small, manageable foraging area that isn't overwhelming for these timid ants. If you are looking for a more permanent home, the Paris formicarium is the gold standard. Its narrow chambers and gypsum-like material provide the perfect texture for the ants to feel secure, mimicking the tight soil tunnels of their natural habitat.

Fun Facts and Advanced Observations

• The Golden Ghost: Because they are rarely seen, Lasius brevicornis is sometimes referred to as a "ghost ant" of the prairies, appearing only for a few hours each year during their spectacular mating flights.
• Subterranean Architects: In the wild, they often line their tunnels with a "carton-like" material made of soil and fungal hyphae, which helps to stabilize the tunnels in sandy or loose soil.
• Chemical Defense: Like other Formicine ants, they use formic acid, but they also produce citronellal and other compounds that give them a distinct, lemony scent when disturbed. This is a common trait among the yellow Lasius species.
• Living Silos: During times of abundance, workers can become "repletes," distending their gasters with liquid food to store for the rest of the colony during leaner times, although this is not as extreme as the true honeypot ants of the desert.