Last week, I found ant species #23.
Formica obscuriventris – aka ant species #23. It’s a mound-building ant of prairies and savannas.
If you’ve followed this blog for a while, you know that we’re trying to inventory the ant and bee species (and others) in our Platte River Prairies. Our main purpose is to see whether or not our restored prairies are providing habitat for the insect species living in our remnant prairies. If they are, it’s likely that we’re succeeding in our attempt to use restoration to enlarge and reconnect fragmented prairies. Last fall, I posted the results of the brief survey James Trager helped us with in the summer of 2012. At that point, we’d found 22 species.
During a prescribed fire last week, we found a big ant mound. The ants were understandably agitated by the fire… I noted the location of the mound and went back the next day with my camera (and my new flash kit!) to get some photos. I emailed James the photos to see if he could identify the ant species, and of course he could – Formica obscuriventris. More importantly, it wasn’t a species we’d found last summer, so I could add it to our list!
The ant mound had multiple entrance holes. There was a lot of activity around this particular one.
The mound was in a restored prairie, which was good to see. Of the 23 species we’ve found so far now, 4 of them are tree-dwellers and 19 are prairie ants. Of the 19 prairie ant species, we have found 14 in restored prairie. I’m hoping we just haven’t looked hard enough to find the other 5 in restored prairie (very possible, given our limited sampling effort so far). If that turns out to be true, it would be a great indication that our restored prairies are acting as new habitat for those ants, and enlarging/reconnecting formerly fragmented prairies.
Ants carrying the carcass of one of their compatriots.
I’m sure many of you could have identified this ant species without James’ help, but I couldn’t and am grateful to him. He pointed out that it’s the boxy cross-section of the clypeus that separates this species from a couple other possibilities. …But you probably already knew that…
Here’s the mound, with a 72mm lens cap for scale.
For those of you interested in the photography side of this, I photographed the ants with a 105mm Nikon macro lens on a Nikon D300s camera. The images above are variously cropped to show the ants better.
It was a partly cloudy day, and the light kept switching from dark cloudy to bright sunny – neither of which was great for photography. To mitigate that, I used a diffuser (thin white cloth on a big collapsable plastic circle about 2 ft in diameter) to reduce the light when the sun popped out and then used flash to fill in the rest of the light needed to use a fast shutter speed. My flash kit is a Nikon R1 Close-up Speedlight system, which has two small flashes – mounted on either side of the lens.
…I might start to like this whole flash photography thing.
The Prairie Ecologist 
When will it be when the Raspberry Crazy ants make up there? They are confined to Texas now, but invasive species move very rapidly. What good thing about the Raspberry Crazy ants is, that they eat the invasive fire ants. But they also feed on the chicks of the endangered Attwater prairie chicken too.
The “Rasberry Crazy Ant” is named after Tom Rasberry who discovered them in Texas and they otherwise have nothing to do with Raspberries. Not that this matters at all, as the species already had a common name when they invaded Florida and along the Gulf Coast as the “Crazy Ant” Nylanderia fulva. They’ve only been in Texas for 10 years, and potentially have been in Florida sometime over the last 50 years (thanks to confusion with Nylanderia pubens). Their distribution thus far seems to be broadly coastal and restricted to the Tropics and Sub-Tropicals.
Where I work we have some red-in-front ants that are slave-takers. Do you know if this one is? Do you know how many of your present and missing ant species are parasites. Some people have speculated (demonstrated?) that healthy populations of parasites and diseases are important components of diverse natural ecosystems.
Stephen – those are excellent questions. I’m going to encourage James to answer them!!
F. obscuriventris is a temporary social parasite, its colony-founding queens requiring a (probably always small) colony of another Formica species to rear their first brood. But this species does not continue to cohabit with a worker force of the host, as do the “slave-maker” species, which by the way, are preferably referred to as cleptergic (work-parasite) ants. It is encouraging to see a parasitic ant species established in a restoration. There is one cleptergic species on Chris’s list already, namely F. pergandei, living with a worker force composed of F. subsericea & F. montana, also from a restoration.
By the way, my sampling at the FermiLab, in your part of the world, Steve, reveals that at least two parasitic species of Formica and a Polyergus species occur in the prairie restorations there.
From the picture of the mound I would have guess the genus correctly, but that is the extent of my knowledge. I love looking at all the ant mounds after a burn, especially to see them get more numerous over time in planted prairies. Maybe it is a false impression, but I tend to think we are making progress when more mounds continue to show up. We have the great big mound builders in our area, Allegheny mound ants.
David
We have a lot of mounds on our place northeast of Ainsworth on Bone Creek. I had no idea there were so many species. Now I want to find out which ones they are.
I’ve been curious about ants in prairies after noticing the huge number of hills visible after burns in Governor Dodge park here in Wisconsin, seems like their sheer numbers must make them a critical yet often overlooked member of the prairie biome, so I was excited where I found your article online. The link to Trager’s paper doesn’t seem to work, though, as well as other links I’ve found online. Is there an up to date link where his research is available? Can you recommend other resources for our homeschooling family to learn about ant/prairie connections?