Ants of the Week: Lasius flavus and Lasius nearcticus

The path to discovery can be encountered in many ways. Take, for example, flipping over a rock in upstate New York last week.

I knew immediately the ants were Lasius (once upon a time called Acanthomyops). I also knew the ants were not Lasius claviger because of something that was missing. Can you guess what?

If you surmised there wasn’t a citronella smell, you are correct. Lasius claviger workers are called citronella ants because of the strong odor they give off. These Lasius were relatively odor free.

Given the size and other characteristics, my guess is either Lasius flavus or Lasius nearcticus.

Lasius flavus is commonly called the “yellow meadow ant.” It is found in Europe, eastern North America, and even into Asia.

Lasius nearcticus is sometimes called the “golden cohabitant ant.” It is found in eastern North America.

According to the key to Lasius of North America found at, the two species can be distinguished by the segments of the maxillary palps. If the terminal maxillary palp segment is longer than the penultimate segment, then the ants are probably L. nearcticus.

I didn’t collect any specimens for further identification. Are there any experts out there that can tell the species from these somewhat blurry photographs?

Lasius are known to tend root aphids and mealybugs. The plump white blobs are root aphids because they have cornicles, the projections at the back of the abdomen.

The root aphids apparently had overwintered with the ants, because the day before it was snowing where I found these. Lasius move the aphids to plant roots where the aphids feed. In exchange, the ants gather honeydew from the aphids. They also are known to eat the aphids, especially in the winter.

That said, I was a little surprised to see this under the next rock I encountered:

This colony had piles of black, oval objects.

I found other similar photographs online, like this one.

Any ideas what the black ovals might be? (The answer will be posted on Friday.)

The reproductives of these two species tend to be darker brown than the workers. Here’s a video of a colony of Lasius flavus.

It would be be interesting to learn more about these two species. Have you ever seen these ants?

For more information about Lasius and aphids, try:

PONTIN, A. J. (1978), The numbers and distribution of subterranean aphids and their exploitation by the ant Lasius flavus (Fabr.). Ecological Entomology, 3: 203–207.

Joachim Offenberg. (2001). Balancing between mutualism and exploitation: the symbiotic interaction between Lasius ants and aphids. Behav Ecol Sociobiol,  49:304–310

Ant of the Week: Thief Ants

Solenopsis molesta:  they are tiny, they are secretive, they are thief ants.

Barely over a millimeter long, you really need a microscope to photograph them. This worker thief ant is running on a piece of cake frosting.

Now that’s better.  (Photograph by © / CC-BY-SA-3.0 retrieved from Wikipedia.)

The workers are often golden yellow-brown in color and may be confused with pharoah’s ants at first glance.

The characteristics of the thief ant worker that you notice under a microscope are the small size of the eyes and the unusual shape of the antennae. Solenopsis (Diplorhoptrum) molesta workers have antennae that are 10 segments long with a relatively large 2-segmented club at the tip. The segments between the scape and the club, the funiculus, are wider than they are long and show darker bands of color, making them distinct.

Some taxonomists have separated the thief ants into a separate genus or subgenus, Diplorhoptrum. Renthal, et al. have found a ring of antennal glands in the thief ants that are also found in other Solenopsis, which they say might be further evidence thief ants are indeed members of the genus Solenopsis.


Thief ants are named for their habit of living near other ant colonies, with tunnels that actually infiltrate their neighbors. The thief ants use the tunnels to go steal brood. They are not looking for free labor like some brood raiders, but use the stolen brood for food. They also feed on seeds and carrion of various sorts.

Solenopsis molesta ants are native to North America. William Morton Wheeler listed them amongst the first native ants to be found in homes.

Vinson and Rao discovered that plots with high levels of Solenopsis molesta colonies prevented new Solenopsis invicta colonies from becoming established. Solenopsis molesta is one of the few ant species that can coexist with Argentine ants, as well. They may be small, but evidently these little gals are tough!

Do you know of anyone working on thief ants? Do they occur where you live?

For more photographs, See:

Series of photographs of Solenopsis molesta by Benoit Guenard
Alex Wild also has captured the tiny thief ants. This one shows the antenna particularly well. Male thief ant with workers from Tucson, AZ.


Robert Renthal, Daniel Velasquez, David Olmos, and S. Bradleigh Vinson (2008), Occurrence of Antennal Glands in Ants. Microsc. Res. Tech. 71(11): 787–791.

S. B. Vinson and A. Rao. 2004. Inability of Incipient Solenopsis invicta (Hymenoptera: Formicidae) Colonies to Establish in a Plot with a High Density of Solenopsis (Diplorhoptrum) Colonies Environmental Entomology 33(6):1626-1631.

Ant of the Week: Solenopsis amblychila

Are you ready for ant season to begin? I sure am! We’ve been having some unusually cold and rainy weather, so the ants haven’t been very active. One warmer afternoon last week, however, I did spot a few ants other than rover ants. They were Solenopsis amblychila workers. Solenopsis amblychila workers are pale, golden yellow. Solenopsis amblychila can tolerate dry conditions. Colonies of this species are found mostly in the Sonoran Desert, that is southern Arizona, southern California, northern Mexico and Baja California, although they do extend further east into Texas as well.

These workers are nesting at one of our local parks, along a sidewalk. The surrounding area is compacted, dry Bermuda grass trampled by thousands of feet. The attraction may be a Solenopsis xyloni colony about a foot away, or may be a nearby ramada full of messy, snacking children.

I found a queen last year, but it met with an accident (also child-related as it turns out) and never had a chance to produce eggs.

Dale Ward has more information and videos of Solenopsis amblychila workers visiting extrafloral nectaries on cactus.

Have you ever seen Solenopsis amblychila? Doesn’t seem like a lot of research has been done on this species.

Ant of the Week: Camponotus novaeboracensis

Have you ever wondered what species of ant is featured in the header of this blog?

This is a worker of my favorite ant species, Camponotus novaeboracensis, the New York carpenter ant. You may have seen the species name written lacking the first a (“noveboracensis“), but the species was originally described as Formica novaeboracensis by Fitch in 1854, so that spelling takes precedence.

The New York carpenter ant can be distinguished from other carpenter ants by its large size (major workers be up to 13 mm long), maroon or red trunk (mesosoma), and sparse pubescence on gaster. Like Camponotus pennsylvanicus, the workers are polymorphic, with the different size classes called minors, medias and majors.

Other similar ants are Camponotus chromaiodes, which has much denser pubescence on the gaster and light red through the petiole, into the first segment of the gaster. Camponotus nearcticus is a smaller species, although the workers may resemble minor C. novaeboracensis workers.

New colonies are founded by single, mated queens. The mating flights usually occur in the spring after one of the first thunderstorms of the season. Each queen digs a small chamber in moist, soft rotted wood or sometimes in the soil (claustral founding). Very rarely nests with multiple queens are found.

This video shows a newly established colony in an artificial ant nest. The large size of the ants, the relatively small colony size (roughly 3000 workers), and lack of sting make New York carpenter ants popular.

Colonies live about ten years. Because they live in cold climates, the colony enters diapause in the winter. The colony must undergo a cold treatment in order to come out of diapause. Colonies held at constant room temperature remain in the overwintering state.

The workers are often found tending aphids and treehoppers on plants.

Similar to many other ants, they also scavenge dead insects.

I notice at AntWeb the name is misspelled. The person who collected the specimens shown could have set the record straight.

What species of Camponotus occur where you live?


Fitch, A. 1854. Insect infesting fruit trees. 1. The apple. N.Y. State Agric. Soc. Trams. 14:  709-808.

Hansen, Laurel D. and John H. Klotz. (2005). Carpenter Ants of the United States and Canada. Comstock Publishing Associates, Ithaca.