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Henry (age 7) asks: “What kind of ants are most common in the Somerville area? Are any of them fire ants?”
I’m glad you asked. Ants are so interesting that I don’t have enough room to say all that I would like to about them.
There are more than 15,000 species of ants in the world, and around 800 in the United States. It is difficult to say which are the most common here; people in our cities on the iNaturalist app post photos of Eastern black carpenter ants and American winter ants the most – so these are certainly among the most common, or at least the most observed.
Eastern black carpenter ants (Camponotus pennsylvanicus) are large – up to three-quarters of an inch long – as well as shiny and black. Carpenter ants bite to defend themselves, but they do not sting like some other ants discussed later. They eat mostly honeydew, a sticky sweet liquid produced by insects such as aphids that feed on sap. Think of sap as the blood of plants: It carries water and sugars from roots and leaves to the rest of a plant. Some insects feed on sap just like mosquitoes feed on blood.
Ants live in large groups called colonies. Each ant in a colony has a job. Workers dig tunnels, clean and repair the nest, feed the young and bring honeydew and other food back to the nest. Soldiers guard the nest entrance and fight off intruders. The queen lays eggs that develop into new ants. In spring and early summer, winged males and females mate. The males die, but the females lose their wings and lay eggs to start new nests.
Carpenter ants are useful. Most nest in decaying trees, where they help the wood to break down. It’s when they nest in damp or rotted wood in homes, sheds, porches or decks that they annoy humans.
American winter ants (Prenolepis imparis) prefer cooler temperatures. You will most likely see these ants in fall, winter and spring. During the summer they rest underground where it is cooler.
Winter ants drink only liquids, especially honeydew, flower nectar and rotting fruit. They also drink from dead earthworms driven to the surface by rain. Worker ants return to the nest and regurgitate the liquid to new, young ants. The abdomens of these young swell to hold more than twice their body weight. These young then ooze a nourishing liquid that the entire colony feeds on during the heat of the summer.
Fire ants. Yes, there are fire ants in our area. European fire ants (Myrmica rubra) are red and tiny – about three-sixteenths of an inch long. They are native to colder, northern parts of Europe and Asia and arrived in this country in the soil of potted plants. They are invasive here because they have no enemies to keep their population in check while pushing out our native species.
They are aggressive, and attack rather than running away. If you move slowly or stand in an area where they are foraging, they will defend their territory by stinging you, causing a burning sensation that can last for hours or longer.
That they sting like bees, with venom, is not too surprising, because fire ants evolved from stinging wasp ancestors.
European fire ants do not build mounds. They live in the soil, under rocks, around tree roots or in decaying logs. They like cool, moist areas – in the shade, often near rivers or lakes. Their nests can contain a few hundred to tens of thousands of ants.
European fire ant populations increase by budding: A queen leaves the nest with some workers. They start a new nest not far from the old one and, in this way, spread slowly outward over larger and larger areas. These populations also spread when people move soil or potted plants with them to new areas.
Not all small, red ants are European fire ants, however. Some are gentler native ants.
There is another species of fire ant you may have heard of. Red imported fire ants (Solenopsis invicta) are native to South America but here are found mostly in the hot, dry areas of the Southern and Western United States. Unlike European fire ants, these “‘Rifa” ants build large dome-shaped mounds that are hard and weatherproof. The size – most are 6 to 18 inches tall and up to 2 feet wide – depends on the size of the colony. A large mound can indicate a colony of up 500,000 ants.
These tiny, reddish ants are aggressive. If a person steps on or disturbs a mound accidentally, thousands of workers will swarm out to defend the colony. They bite to hold on to a person’s skin and use their stinger to inject painful, burning venom multiple times, so an interloper might get hundreds or even thousands of itchy, burning stings – though at least the itching usually goes away in about an hour. (If a person is allergic to the venom, they need to see a doctor right away.)
If a fire ant mound gets flooded, the ants will hold on to each other and form a large floating ball of living creatures. This ant raft can float for up to 12 days until it finds higher ground. If you see a raft of fire ants, stay away! They feel threatened and will deliver higher doses of venom if you disturb them.
The good news for people in Massachusetts is that red imported fire ants do not survive cold weather. Tennessee is about as far north as you can find them, and even in Tennessee they sometimes die out during cold winters.
Other commonly seen ants in Massachusetts include odorous house ants (very stinky), pavement ants (found in sidewalk cracks) and field ants (found in fields and grassy areas).
Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.
Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.
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