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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?

References:

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.

2

Last week I flipped over a rock about six inches square and found this:

xyloni-seed-storage

Okay, it doesn't look like much until you zoom in closer.

solenopsis-seeds-dvap

The grayish-mound is a solid mat of oval, wrinkly seeds. Apparently they had been gathered and stored by the Southern fire ants (Solenopsis xyloni) you see running around. The ants were in full defensive mode.

The seeds were both on the ground and on the underside of the rock, so there was quite a mass of them.

 

seeds-in-cache

 

Seeing the seeds reminded me of an earlier time (above photograph) I had found a similar cache of seeds under a rock . At the time I didn't know what plant they were from, but now I have figured it out.

These seeds are from a type of ground spurge, Chamaesyce prostrata. Another common name is sandmat. (See post about Southern fire ants and sandmat).

The University of Arizona has an illustration of the plant in their older weed manual under the name Groundfig Spurge, Euphorbia prostrata. See the seed labeled "d" in the illustration?

A quick search of the internet revealed the UC IPM website states "Weed seeds, particularly spurge, may attract the ants away from the bait..." This statement is referring to Southern fire ants in almond groves.

Seems like there might be something worth investigating going on here.

Have you ever seen Southern fire ants with seed caches? What kinds of seeds did you find in them?

3

The ants are still active here, but I haven't had much to report. In an effort to get back in the swing of things, I will be posting some short notes.

Do you know what this is? I tipped over a rock near a Southern fire ant nest and found this cache of tiny seeds. It is easy to forget that fire ants also harvest seeds.

I should have picked up a couple of the seeds to try to sprout them. It wasn't obvious where they came from, as there weren't any plants nearby.

Have you ever found seed caches in fire ant nests?