Harvester Ant Middens with Isopods

You can tell a lot about a society by what its members throw away.

Take these harvester ants, for example.

Your eye might be attracted by the flurry of activity around the nest entrance.

It does pay to look elsewhere, though.

Here’s the trash heap. Looks like these ants have been gathering a lot of Isopods, otherwise known as rolypolies.

This midden was extensive, and strewn with Isopods.

As an entomologist, my eye was drawn to the beetle elytra (hard upper wings).

Here’s another beetle.

The harvester ant mound was along a trail at Boyce Thompson Arboretum near Superior, Arizona.

About 1/2 mile away, I spotted another mound of the same species.

This one seems to have more plant material, plus a bit of egg shell.

Still a lot of Isopods, although the exoskeletons are more broken up. There’s an elytra of the same kind of beetle as was on the first harvester ant mound.

There’s another elytra.

It felt good to get out and see some ants, although the time was much too brief. I would like to have looked around more thoroughly.

And, oh yes, there were a few flowers too.

Did you get to do any hiking this weekend?

Test Tube Ant Nest

I often get questions about raising ants. How do you keep a colony disease-free and growing in an artificial nest?

One of the most common ways to keep ants is in a glass test tube nest. The advantages are that glass tubes are easy to clean, supply the proper moisture, convenient to transport and can grow in number as the colony grows.

1. Obtain a glass or plastic test tube. The size depends on what kind of ants you are keeping. You can find test tubes at most scientific supply stores.

2. Fill roughly 1/3 way with water. Use clean, good quality water.

3. Roll up a sterile ball of cotton and shove down to the top of the water surface. The idea is to keep the water from flowing out, but create a humid chamber for the ants by creating a tight plug of cotton. Push the cotton down with a clean probe or skewer. See that the moisture does not come past the top of the cotton plug. If it does, pull out the plug and try again with fresh cotton.

You can set the test tube in a plastic bin rimmed with fluon, a milky teflon-like substance that keeps ants from crawling away (see below). Or you can start out by plugging the tube with cotton to keep the ants inside.

Once the number of workers increases, you can add more test tubes.

For more information try:

How to Make An Ant Farm

Instructions For Building Artificial Ant Nests

How to Feed Queen Ants

Where to Get Fluon

AntsCanada Ants Store

Ant of the Week: Dorymyrmex bicolor

Dorymyrmex bicolor ants are common in Arizona, especially in open areas. In a previous post, I wrote about how to identify them.

A few weeks ago I visited an agricultural research station and found almost a monoculture of Dorymyrmex.

The first thing you notice about Dorymyrmex bicolor colonies is their neat circular mounds. (Most of these were conveniently located along the dirt roads.)

Each reflect the color of the soil beneath the surface. This one wasn’t a perfect circle.

Nor this one.

Tofilski and Ratnieks (2005) studied the mound formation of two colonies of Brazilian Dorymyrmex. They found the worker ants removing excavated material from the nest deposited their loads at the crest of the mound and beyond, preventing the material from rolling back into the entrance hole. They also indicated that workers maintained the circular shape, when one side was removed, by climbing the area with the least slope to deposit their loads.

Ratnieks noted that ants of other, larger species had difficulty climbing the mounds, thus suggesting the mounds served a protective function.

As you will see in the next few photographs, the Dorymyrmex were carrying out clumps of soil and related materials the morning I visited.

Because ants at all the mounds were so busy removing material, I began to wonder about it. Were the clods of soil and pebbles rolling into the entrance hole over night? Perhaps there had been a wind storm or vehicle disturbance?

By the way, you might recognize these ants under a different name. Prior to a revision of the genera, Dorymyrmex bicolor was known as Conomyrma bicolor. Under that name, they had a brief burst of limelight when Möglich and  Alpert (1979) found they exhibited tool use by dropping small stones on their competitors, particularly Myrmecocystus workers. Finding ants that stoned their enemies caused quite a stir, as you can imagine.

Thinking about that, I also began to wonder if perhaps Dorymyrmex bicolor worker ants also drop stones on conspecifics, that is other Dorymyrmex bicolor nests. With the name change, it is somewhat hard to track the literature. Does anyone know? Anyone studying Dorymyrmex bicolor?

If not, perhaps it would be worthwhile to visit these fascinating ants some evening.


Adam Tofilski and Francis L. W. Ratnieks. (2005). Sand Pile Formation in Dorymyrmex Ants. Journal of Insect Behavior, 18(4): 505-512.
.pdf will load immediately at http://www.cyf-kr.edu.pl/~rotofils/tofilski_ratnieks_2005.pdf

Michael H. J. Möglich and Gary D. Alpert (1979). Stone Dropping by Conomyrma bicolor (Hymenoptera: Formicidae): A New Technique of Interference Competition. Behavioral Ecology and Sociobiology, 6 (2):  105-113.
free .pdf available at Springer

Rover Ant Condo

In an effort to learn more about rover ants, I have been searching for nests.

During the summer, we accidentally discovered several colonies when transferring potted plants, so we know they nest in those. We also watched a colony relocate from one nest in the soil to another. It was cool to see the big gush of ants along the trail as the queen and her entourage moved through.

This week I found another place where some rover ants are hanging out.

From a few feet back, it doesn’t look like much. This is an old stalk from a hollyhock. Hollyhock stems are filled with a soft, white pithy material.

It doesn’t look much more significant close up.

If you watch for a few minutes, however, it becomes apparent that some ants live here.

Note to self:  investigate that beige shiny stuff around the entrance. Any ideas?

This one seems to be eliminating something. I wonder if that has anything to do with the shiny material?

Most of these are fairly light-colored workers. It is also about 50 °F and shaded for the most part, so activity in the entire yard is way is way down. We’ll see what happens as it warms up again.

By the way, the shape of this entrance leads me to suspect it was once created by another insect.

This is the entrance of the small carpenter bee, Ceratina that I found nesting in the hollyhock stalks earlier. If the entrance above is one created by a carpenter bee, then the ants have closed it up a bit.

So, is this a nest or some sort of bivouac? What do you think?