Pest spotlight: Central European bicolored ant, or ‘ManhattAnts’

ManhattAnts are fast walkers with good vision, which researchers theorize helps them navigate smooth stone and concrete habitats in urban areas. (Photo: Donat Agosti, Specimen: CFH000014, from www.antweb.org)

The Central European bicolored ant (Lasius emarginatus) has been in the U.S. since at least 2011. But its population in New York City has grown so much in recent years that it is tied for No. 1 pest ant with pavement ants (Tetramorium immigrans). The volume increase has led it to be nicknamed ManhattAnt, with a dedicated website to determine its spread. Another nickname is the New York Ruffi-Ant.

In Europe, it’s a forest-focused species that contents itself with soil and leaf litter, although in some areas it is known as a house ant.

In the Big Apple, it’s expanding its territory by about one mile each year — living its best life in sidewalks, urban flower planters and anywhere honeydew is available. Because of its speed and unusual (among ants) habit of climbing vertical surfaces in which to nest, researchers predict the species could expand from Portland, Maine, to Atlanta, Ga. iNaturalist already discovered established populations in New Jersey.

ManhattAnts are seemingly aggressive toward other ants, including among neighboring ManhattAnt colonies. They move fast and forage day and night, even during rain events where tree bark is dry, according to researchers. The “bicolored” moniker stems from its reddish-orange body and dark brown head and gaster (backside). Its genus name, which covers several species of cornfield, moisture and (through the subgenus Acanthomyops) citronella ants, means “fuzzy or hairy” in Latin; one of the most common Lasius species in the U.S. to date is L. interjectus, the large yellow ant.

A paper published in May on ManhattAnts points out that it’s important to learn as much as possible about the ant’s behavior in the U.S., as it differs somewhat from that in Europe and other locations.

“New York City has been the site of introduction for some of North America’s most damaging invasive pests — both chestnut blight and the Asian long-horned beetle were first identified in New York City, which are together responsible for the deaths of an estimated 4 billion trees… It is essential that emerging pests, such as the ManhattAnt, are correctly identified and monitored after they are first discovered,”
report the researchers, who also are behind the Project ManhattAnt’s website.

The study was led by Clemson (S.C.) doctoral student Samantha Kennett last year while a graduate student at Kennesaw (Ga.) State University. The team identified three characteristics that could make ManhattAnts a serious pest:

1. A high volume of the ants have been increasingly reported as pests inside human dwellings.
2. They tend to score honeydew from scale insects and aphids, which could have negative impacts on urban trees.
3. L. emarginatus workers have been seen surrounding and dismembering pavement ant workers (T. immigrans) in sidewalk habitats where both species are abundant, the researchers’ observations show.

As a humorous aside, they noted, “One colony of L. emarginatus was even found nesting in a small flower planter in the middle of Times Square, far away from street trees or large ornamental plants that would typically serve as nesting habitat. Often, the only visual ‘non-humans’ in Times Square are humans dressed as Disney animals and yet, hidden in this flower pot was a whole society of animal beings.”