In N.Y.C. Apartments, the Ants Go Marching Up

Over the last decade, the teeny Lasius emarginatus — which has a reddish-brown thorax and a dark brown head and abdomen — has been absolutely thriving in New York, and has been nicknamed ManhattAnt.

“My research focuses on understanding how this ant, who is now one of the most common ants in New York City, has been able to be so successful, surviving in highly urban habitats,” said Ms. Kennett. She found Lasius emarginatus in the trees all up and down Broadway, as well as in midtown. “We found them in Times Square,” Kennett said. “They are everywhere.”

Including, apparently, the upper floors of apartment buildings. Like many ambitious New Yorkers, the ManhattAnt is upwardly mobile. “It forages in trees,” Ms. Kennett said. “It climbs a lot. They found it in second story buildings in Europe.” Now, as it expands its habitat, it appears to be scaling the structures of New York City.

Upon examining photographs, Ms. Kennett was able to confirm that Mrs. Russell Paige’s ants and this reporter’s ants were indeed Lasius emarginatus. Ms. Guhl did not have photos, could not be sure of the species that visited, and has since disposed of the bodies. “I wasn’t exactly looking super carefully at them,” said Ms. Guhl.

Just how high Lasius emarginatus will climb is unknown. Ms. Kennett started an online initiative, Project ManhattAnt, and she hopes that New Yorkers will report their sightings to help scientists track the industrious insect as it silently spreads: “We’ve started to see populations pop up in New Jersey and as far as Long Island.”

Dr. Rob Dunn, a professor in the Department of Applied Ecology at North Carolina State University, whose team is credited with discovering Lasius emarginatus was living in New York, believes any ManhattAnts New Yorkers see inside are probably looking for water — and are likely not there to stay. This ant “nests in the ground,” he said. “It nests under logs and in all the studies we’ve done, it prefers to have some natural habitat.”