Last week I flipped over a rock about six inches square and found this:
Okay, it doesn’t look like much until you zoom in closer.
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.
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?
2 Replies to “Solenopsis xyloni Stores Spurge Seeds”
Interestingly, I wrote a blog about the same phenomenon – I found the seed piles under dry cow manure and also ended up with our little fire ants as the solution of the mystery http://arizonabeetlesbugsbirdsandmore.blogspot.com/2014/10/mysterious-piles-of-silvery-graines.html
Thank you for sharing the link to your blog post. I will definitely be on the look out for the amber seeds, too.
It is interesting the color variation in the southern fire ants.