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Henry, 7, asked such interesting questions about ants last week that I had to continue the discussion. Besides the creatures already discussed – carpenter ants, winter ants and fire ants – Massachusetts (and the world) are home to a wide array of others. All have some things in common.
Ants live in groups called colonies. Most colonies have a queen that lays eggs. The ones that are fertilized develop into females, all of whom are sisters; the unfertilized ones develop into males. The vast majority develop into daughters (the workers). In the spring or fall, a small number of winged males and new queens leave the colony to mate and start new colonies.
The queen ant can live for 20 or 30 years. She mates once – when she is only a few weeks old – and stores the sperm for the rest of her life. Her offspring usually live for about a year, but she keeps producing new offspring for the colony for as long as she lives. When the queen eventually dies, the workers keep working, but there are no new ants being produced. Eventually all the workers, and therefore the colony, die. (If you have ever had an ant farm full of worker ants without a queen, you have seen this decline firsthand.)
Male ants die after mating, but the new queens lay eggs to start new nests. The eggs hatch into larvae that are almost too small to see but grow and grow, molting four or five times. Eventually they enter the pupal stage and metamorphose into young worker ants. These young help inside the nest, feeding and caring for the eggs, larvae and pupae. When they are older, they forage outside the nest, looking for food to bring back. When the colony is big enough, it produces males and new queens to start the process over again.
Have you dropped food on the ground only to notice hours later that it is covered in ants? How did all of these ants learn that this food was there? Surely, they didn’t all stumble upon it by accident?
Not all. Ants communicate with each other by leaving behind a scent trail when they forage. Ants read these chemical scent trails with their antennae. As more and more ants follow a scent trail, the scent become stronger and stronger. This encourages even more ants to follow. Soon the food is covered in ants. When the food is gone, fewer and fewer ants return to the location. Eventually the scent trail disappears.
Ants in a nest recognize their nest mates by chemicals that cover their body. When one ant touches another with its antennae, it smells the other. Ants without the right body chemicals are enemy ants that are not be allowed into the nest.
There is no central control in a colony. The queen does not tell the workers what to do – they just do what needs to be done. Likewise, workers do not tell others what to do.
Ants work together to help the colony survive. Some people think of an ant colony as one superorganism in which all function together to help the entire colony survive, similar to how cells in our brain or body work together.
For example, if ants need to pick a new nest site, many workers may go out to scout. If one worker finds a suitable site, she returns and sends out a chemical message: “Follow me.” A second ant follows her to the site. If they both like the site, they return and send out a message: “Follow us.” The process builds. If enough ants visit and like the site, the group will return to the old nest and bring a new queen to the new nest site.
Ants also work together to defend themselves. Last week, I discussed how fire ants swarm and sting when their nest is disturbed. Other ants are more peaceful, though, and some might even be considered farmers.
Leafcutter ants, for example – they cut pieces of leaves to bring back to the nest but do not eat them, instead using them to grow a fungus that serves as their food. Young worker ants clean and take care of the fungus. They also take care of the eggs, larvae, pupae and queen, which live in tunnels in the fungus. Some worker ants remove all the waste and dead organisms to garbage chambers down deep in the ground. These trash workers, who touch many kinds of bacteria and molds, avoid contact with the fungus and the ants living in the fungus. They do not want to contaminate their food source.
Some of the more common types of ants in Massachusetts are odorous house ants (Tapinoma sessile), also called stink ants, coconut ants or sugar ants. These tiny, hardy ants are only one-eighth-inch long, dark, not too sensitive to heat or cold, and they like the sugary or greasy food found in our kitchens and pantries. If you crush one in your fingers, it smells. Some people say these ants smell like rotten coconuts; others blue cheese, rancid butter, turpentine, Pine-Sol or other cleaning products. In one public sniff test at a North Carolina Bug Festival, people crushed an odorous house ant, smelled it, and selected one of four smells to best describe the odor: rotten coconut, rancid butter, blue cheese or other. Of 143 responses, 38 percent opted for blue cheese, 25 percent rotten coconut and the rest other choices – mostly cleaning products. (I have been overrun with these ants in my kitchen this year, and I am in blue cheese camp.) The researchers also let a coconut rot, and discovered that a moldy, rotten coconut smells like – what else? – blue cheese.
You might see pavement ants (Tetramorium caespitum) in sidewalk cracks. They are widespread in residential areas because of the many sidewalks. These small, dark ants are about one-eighth inch long. They often nest in soil under pavement cracks.
You might find field ants (Formica spp.) outdoors in lawns and fields. They do not venture indoors. They are medium-sized ants – about a quarter of an inch long. They build mounds and feed on insects and honeydew. They might bite you if disturbed, but they do not sting.
There are more than 14,000 species of ants, but only about 50 have been well studied. Henry, if you want to enter a scientific field with a lot of room to grow, consider studying ants.
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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