Swimming By Carpenter Ants

If you have a pool, you know that most insects don’t have a chance if they fall into the water. Here at Wild About Ants, however, we know ants often do the seemingly impossible. To prove it, let’s look at the ability of certain species of ants to swim.


In a recent article in Myrmecological News, Gora et. al. reported on their investigation into swimming by the carpenter ant, Camponotus pennsylvanicus. They found carpenter ants use vision to find escape platforms from the water. One hundred percent of the control ants placed in the water of the test apparatus were able to swim to the edge and get out of the water successfully. Ants with their vision occluded, on the other hand, failed to exit the water.

Although this study focused on ants swimming as a method to escape from water if they fall in accidentally, some Camponotus ants in pitcher plants are able to actively swim to capture mosquito pupae for food.

As you might expect, ants that live in areas that are regularly flooded by tides, such as ants living in mangrove swamps, are particularly good at swimming.

This video from Life in the Undergrowth shows mangrove ants running across shallow water and then at about 1:02 minutes actively swimming in the water. Notice how the swimming ant holds its hind legs out behind it like a rudder.

Yanoviak and Frederick tested 35 species of tropical forest ants to see how many had the ability to move through water in a directed way. Of those, ten species were able to show rapid directed movements and ten more exhibited slower, but directed movements. The remaining species apparently needed tiny life jackets.

The bottom line is that although different species of ants vary in their ability to swim, some are quite adept at it.

Previous Posts at Wild About Ants:


Gora, E.M., Gripshover, N. & Yanoviak, S.P. (2016) Orientation at the water surface by the carpenter ant Camponotus pennsylvanicus (De Geer, 1773) (Hymenoptera: Formicidae)  Myrmecol. News 23: 33-39. (Let me know if the link doesn’t work and I’ll find it for you.)

S. P. Yanoviak, D. N. Frederick (2014) Water surface locomotion in tropical canopy ants. Journal of Experimental Biology 217: 2163-2170; doi: 10.1242/jeb.101600

Carpenter Ants Under Glass

Some recent shots from my travels:

First of all, for the person who asked about the red spots in their ant farm. Do the spots look anything like the red dot on the middle leg on the left side of this photograph?  That is a mite.

The ant is a winged Camponotus pennsylvanicus “princess.”

I don’t usually manipulate the ants I photograph, but these were in a log that had been split for firewood, so I thought I’d play around with holding them in and under glass.

Camponotus pennsylvanicus ants are more cooperative than most.

I kind of like the results.

What do you think?

Ants in Winter: Part 1 Camponotus in Diapause

Last week I got a peek at where Camponotus pennsylvanicus carpenter ants spend the winter.

The temperatures were hovering around freezing in upstate New York, where I was helping someone spit firewood.

When the wood split, occasionally we would find tunnels, hardly more than grooves in the wood, packed with ants. Although the ants look like they might have been moving, they were mostly stiff and inactive. You could shake them out onto the ground without much resistance.

This group was in softer wood with more decay. Notice the larva. Most of the clusters of worker ants had small larvae with them.

Camponotus carpenter ants that live in temperate climates enter a state of slowed metabolism, called “diapause”, in the late fall and through the cold parts of the winter. Generally, the queen stops laying eggs. The workers begin to aggregate more than before. The workers develop large fat bodies, which can be seen as their gasters swell in size, as well as produce glycerol. Glycerol is an alcohol that helps prevent the formation of ice crystals within the ants’ bodies. No wonder the ants stagger a bit when they try to move. 🙂

What are ants doing this month where you live?

For more information try:

Cannon, C. A. 1990. Demography, cold hardiness, and nutrient reserves of overwintering nests of the carpenter ant, Camponotus pennsylvanicus (De Geer). M. S. Thesis, Virginia Polytechnic Institute and State University. 165 pp.

Cannon, C.A. and R.D. Fell. 1992. Cold hardiness of the overwintering black carpenter ant. Physiol. Entomol. 17:121-126.

Ant of the Week: Camponotus pennsylvanicus

A few months ago I put up a post asking people to guess which states I had visited this summer based on the species names of the ants in the photographs.

If you had guessed Pennsylvania for this one, you would have been correct. Camponotus pennsylanicus colonies are found in a number of states throughout the East and Midwest, as well as Pennsylvania (Hansen and Klotz, p. 86). The ants in the photograph are in upstate New York.

Colonies of these ants are often found in wooded regions and Camponotus pennsylvanicus workers are commonly called black carpenter ants because of their habit of making nests in wood, such as stumps or rotting logs.

How do you tell a Camponotus pennsylvanicus worker from this Formica worker? Two characteristics that are relatively east to spot are the long blonde pubescence (hairs) on the gaster (rear section) of the Camponotus. The trunk (middle section) is evenly rounded when seen from the side for Camponotus, whereas there is a notch or valley in the Formica.

How do colonies start? The alates fly in the spring, usually on the day of the first spring thunderstorm. After mating, the queen pulls off her wings (you can see the wing scars on the side of her trunk) and starts her own nest, often under the bark of a fallen log like this one.

The males look more like wasps. The males die after the mating swarm.

The workers are polymorphic, ranging from 6-13 mm in length. Although the largest workers are sometimes called soldiers, they do much more than defend the nest. They also are involved in nest construction and foraging.

Carpenter ants do not have a stinger, but can bite to defend themselves.

The tasty red fruit is a mulberry. Camponotus workers often gather sweets from fruit, nectaries, extrafloral nectaries, and honeydew from other insects.

They also prey on or scavenge a number of different arthropods. For example, a recent study has shown Camponotus pennsylvanicus to be a predator of the red oak borer, Enaphalodes rufulus, a cerambycid beetle that was associated with oak decline in the Ozarks (Muilenburg et. al., 2008). Unlike harvester ants, Camponotus workers carry virtually all the food back to the nest internally (Cannon and Fell, 2002).

I wonder if they are going to find that caterpillar at the base of the bud.

Due to their large size,  carpenter ants are much easier to see and study than rover ants!


Cannon, Colleen A. and  Fell, Richard D. (2002). Patterns of Macronutrient Collection in the Black Carpenter Ant, Camponotus pennsylvanicus (De Geer) (Hymenoptera: Formicidae). Environmental Entomology. 31( 6):  977-981.

Muilenburg, Vanessa L., Goggin, Fiona L., Hebert, Stephanie L., Jia, Lingling and Stephen, Fred M. (2008). Ant predation on red oak borer confirmed by field observation and molecular gut-content analysis. Agricultural and Forest Entomology, 10(3): 205-213.

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