Entomologists catalog over a thousand species of ants that live in North America, many of which live in Iowa on Owl Acres. Each species has its own fascinating way of doing life. Let’s take another look at the ants that have been crawling all over the peonies. They are called winter ants or false honeypot ants, (Prenolepis imparis).
Winter ants are found throughout North America. As their name suggests, they are unusual in their preference for cooler, even cold, weather for foraging. This gives them a competitive advantage over their warmer-weather rivals. They are active when the temperatures aboveground are between freezing and 60 degrees.
Like other ants, winter ants live in colonies. They build their colonies deep under ground by excavating a vertical shaft that reaches eight to eleven feet deep, well below the frost line in northern climates. Then the ants construct chambers that open off the central shaft, beginning about 24 inches below the surface. As the colony grows, more chambers are created or enlarged. Over a period of eight or nine years, the colony may grow to house up to ten thousand members. These members include one to several queens, some males, and the rest worker ants. The worker ants are defined in two cohorts, those hatched this fall, and those hatched a year ago. Each ant has a specific job.
The queen’s job is to lay eggs, so in January or early February, the males and females come out of their nests and swarm on low-lying brush and tree trunks in a mating frenzy. The queens are reddish-brown and twice as big as the little black males. Their size doesn’t deter the males from their conquest even though once they’ve mated, they’re doomed. When they’ve had enough, the queens fly away to find their home nest or to start a new one. For the next eight or nine months, they’ll take their royal place, being waited on and fattened up by their workers. In about September, they’ll get around to laying their eggs. Within a couple of months, a new generation of ants will emerge first as larvae, then as pupa and finally as adults.
These newest members of the colony have an unusual role to play in the nest. They will spend the next ten months as food storage tanks. The older ants go out foraging for food and bring it back in their social stomachs. They don’t have honeycombs or anything to store it in, so they transfer it to the young workers. The young workers accept the food, holding it in their social stomachs called gasters. They are called corpulents at this point because the gaster swells with the food and they weigh up to four times as much as the older workers. They serve as storage tanks until their load is needed to nourish the nest. By the time they are ten months old, they have used up their stored food and graduate to the foraging workers guild. During their second year they are the ones gathering the food and storing it in their younger relatives.
This food storage system is necessary because when the weather warms up, the winter ants retreat to their nests, plug up the entrances and stay down there estivating through the summer and into the fall. They rely on the stored food to survive the summer.
Winter ants aren’t very picky about what they eat. It might be the nectar from the peonies today and the fluids from a dead earthworm tomorrow. They prefer fatty foods in liquid form that they can bring back to the ant colony. Once they’ve located a source of food, though, they will defend it against all interlopers until it’s gone. In the case of the peonies, this creates a mutually beneficial relationship.
Winter ants don’t harm people. They don’t want to be inside, and get there mainly by accident. They disappear when the weather warms up, and experts recommend simply leaving them alone to do their thing. As well as protecting the peonies, their “thing” includes aerating the soil and cleaning up dead things. Sounds like good neighbors to me.
Photo by Alexander Wild. Alt text: Winter Ants in a colony chamber. Two have distended abdomens which are filled with liquid food. Another carries a mass of white eggs in her mandibles.