Here’s an interesting video for you of some interactions between fire ants (the invasive ant species closest to my heart) and a newly invasive ant species beginning to spread across Texas. Rasberry crazy ants (Nylanderia sp. nr. pubens) were first noticed in the Houston area around 2002. (For people who don’t keep up with the world of ant taxonomy, most of the genus Paratrechina was moved into Nylanderia in 2010.)
Crazy ants take their name from the way in which they run about very quickly while turning frequently. The common name is applied to a number of ant genera. As you can see in the video these ants are fast. I’ve personally witnessed another invasive “crazy ant” (Paratrechina longicornis) fall into my fire ant colonies and become trapped many times. Although they can’t climb out again and they are vastly overnumbered they’ll hang out in little groups by the water tube for days, apparently too fast for the fire ants to catch. Trying to squish them is like playing whack-a-mole. They also got into the sterile buffer and the coffee.
Thanks to Danny McDonald for providing the Rasberry crazy ants and helping to referee their valiant battle. Danny is one of the few researchers working in this system right now.
6legs2many 
I’m still not sure which are the fire ants and which are the crazy rasberry ants. They all look fast to me. And what the heck are they doing when they shake their tails around?
I have very clear memories of our former post-doc, Shawn, showing me acrobat ants in the field, and explaining how they had heart-shaped abdomens. And I remember nodding and smiling and thinking ‘I have no idea what you’re talking about those look like all the other ants.’
But now they look completely different to me, so go figure.
Anyway, the crazy ants are a bit lighter and greyer and they tend to turn more as the move (run in circles). They also have longer more spidery legs. They’re the ones that zip on and off the screen practically before you know they’re there.
When the fire ants shake their abdomens they are “gaster-flagging.” In lots of insects this acts as a visual warning signal and/or helps spread alarm pheromones. Also, fire ants will often extrude a drop of venom on their stingers and this will get the venom into the air.
i couldn’t tell the fire ants from the raspberry crazy ants either…interesting vid though
Yeah, it can be a bit tricky until you get an eye for it. I still remember the first time the lab post-doc was pointing out the differences between fire ants and acrobat ants for me and I staring at them thinking “these look EXACTLY THE SAME.”