Solenopsis xyloni and Forelius mccooki: Nosy Ant Neighbors?

A few ant nests dot the sides of a walking pathway at a nearby park, so of course I have to check them out.

For the most part the nests are small colonies of southern fire ants, Solenopsis xyloni.

There are also seemingly endless streams of Forelius mccooki workers traveling along the concrete edgers and sidewalks.

While taking photographs of the fire ant middens, I noticed the fire ants had a few visitors standing by an entrance hole.

Millimeters away from the fire ant workers stood two Forelius workers.


Curious, I watched for some minutes. The fire ants did not approach the Forelius, and the Forelius remained relatively still. They didn’t appear to be investigating the middens.

The Forelius had a nest entrance not too far away. Perhaps they were just nosy neighbors? (I did notice there weren’t any Solenopsis visiting them.)

Wayne Armstrong suggests perhaps the relationship isn’t entirely benign. In this video, Solenopsis xyloni workers flag their gasters in response to Forelius pruinosus workers encountered at an artificial feeding site. (You will notice the coloration difference between our local S. xyloni compared to his California ones.)

Interestingly, the soldiers don’t seem to respond. According to his notes (scroll down to Southern fire ant), the Forelius were ultimately successful in overtaking the food.

Ants of the Southwest has a photograph of a Forelius worker spraying a S. xyloni worker. He reports S. xyloni exoskeletons piled in Forelius middens, which is also reported here.

Even though southern fire ants are chemically well defended, perhaps they are no match for Forelius.

Have you ever encountered these two species?


Obin, Martin & Vander Meer, Robert. (1985). Gaster flagging by fire ants (Solenopsis spp.): Functional significance of venom dispersal behavior. Journal of chemical ecology. 11. 1757-68. 10.1007/BF01012125.

New species for the blog: Neivamyrmex Raiding Dorymyrmex bicolor

People who go to u-pick vegetable farms usually come home with lettuce or corn or tomatoes. When I went to a u-pick vegetable farm near Phoenix, Arizona, I came home with photographs of ants, instead.

It wasn’t surprising to see numerous circular mounds with a single entrance hole in the center.

The nests are made by a common ant in the low desert, Dorymyrmex bicolor. As I’ve written previously, D. bicolor seems to prefer to nest along dirt paths or roads. The garden had plenty of those.

Here’s another nest, again with an entrance hole in the center, and covered with active ants.

The workers here were pulling out clumps of what looked like dirt. Can you see the single petiole that is characteristic of the species?

After seeing about three dozen or so circular nests like those above, I found this one.

Same rough shape, but notice anything different?

Where are all the ants?

From another view, the entrance hole is actually blocked with dirt.

Finally, I can see some ants, but those aren’t Dorymyrmex bicolor workers.

The workers exiting from this nest are uniform in color. They have a petiole and a postpetiole.  Notice anything else about them?

The Dorymyrmex worker ants from the same perspective have large eyes. See any noticeable eyes from this view?

Having no noticeable eyes is a characteristic of Neivamyrmex army ants (Note:  They do have a single eye facet, but it isn’t obvious.)

The exact species is much more difficult to figure out.

Wayne P. Armstrong found some similar Neivamyrmex near the Superstition Mountains in Arizona, which are close to the farm where I found these ants. Gordon Snelling identified Armstrong’s ants as Neivamyrmex leonardi. The ones I found could be N. leonardi or one of several similar species.

In any case, Neivamyrmex army ants resemble their larger namesakes because they are always on the move. They don’t make permanent or long term nests like the Dorymyrmex, but instead raid nests of other ants stealing the brood for food. Seems like in this case a Dorymyrmex bicolor colony was a target of their raid. Armstrong reports Neivamyrmex workers raid Pheidole nests, as well.

So, I didn’t bring home lettuce, but maybe something even better from the u-pick farm.

Have you ever seen Neivamyrmex army ants?

Ants Tending the Aster Hopper, Publilia concava

Time to knock the cobwebs off this blog with some new posts. Let’s start by taking a look at ants tending the aster hopper, Publilia concava.

This species of treehopper is relatively easy to find because the nymphs feed in aggregations on the underside of goldenrod leaves (Solidago altissima).

The relationship between ants and aster hoppers is a mutualism. The ants guard the treehoppers and drive away predators. In this case the ants were Formica sp.

In return, the nymphs supply food for the ants in the form of liquid honeydew. In the center of the photograph the nymph has curled its tubular abdomen to present food to the ant.

The adult female treehoppers lay their eggs in clusters and guard them until they hatch. Then the worker ants take over. In a recent study, Morales and Zink found adult female treehoppers with ants tending them were more likely to lay eggs than untended ones. At one site the researchers discovered egg laying per treehopper actually increases with the number of worker ants nearby.

If you’ve never watched ants tending aster hoppers, here’s a short video. (Unfortunately, the lighting conditions weren’t ideal and there was a breeze.).

You might think that the treehopper nymphs, as phloem feeders, would be rather sessile, but the nymphs move around more than you might expect. Morales and Zink suggest that treehoppers may respond to density of conspecifics as well as ants.

In any case, the relationship between aster hoppers and ants is an interesting one.

Have you ever seen aster hoppers tended by ants?


Morales MA, Zink AG (2017) Mechanisms of aggregation in an ant-tended treehopper: Attraction to mutualists is balanced by conspecific competition
PLOS ONE 12(7): e0181429.

Morales, 2002. Ant-dependent oviposition in the membracid Publilia concava. Ecological Entomology. 27:  247-250. (download .pdf)

Previous post about the treehopper on thistle, Entylia carinata

Rover Ants of Rush Milkweed Flowers

The rush milkweeds are flowering.

The open flowers attract an array of insects.

For example, tarantula hawks seem to prefer milkweed flowers. In fact, they are one of the chief pollinators of the plant.

No surprise that rover ants also visit.

From the swollen appearance of the metasoma of the upper ant, it looks like the worker ants are feeding on nectar.

Wait, the nectaries aren’t open on these buds.

It can be hard to think of something as small as a rover ant as a predator, but they do catch insects like this thrips.

The tarantula hawks, on the other hand, probably aren’t in any danger.