July 30, 2007
by: jovial_cynic
Formica Obscuripes

As a kid, I played with red-headed ants all the time, knowing that they were the most aggressive ants we have around here in western Washington. My friends and I would capture them and put them in a jar with a wasp and watch in fascination as the ants would clasp onto the wasps legs and wings and not let go. The wasp would bite a few of the ants, killing them, but would eventually be taken down and overcome.

The red-headed ants could take on anything - wasps, beetles, roly-polies, worms - it didn't matter. They do this "death grip" thing, where they bite down and don't let go until their prey stops moving.

Today, I learned something else.

Formica Obscuripes uses their acid to signal attack. I captured a couple of them (I'm still at work without my camera) and tossed them into a jar. Within seconds, I could feel moisture on my pointer finger as the captured ants spit on me, and seconds later, there were hundreds of these red-headed ants coming after me, following the movement of my hand as I went to pick them up. And the smell is strong - it smells just like vinegar and tastes like it too.

Anyhow, I've got a jar of about 10 of them that I'll take home and video fighting against some large predator. And if the weather holds up, I'll bring my camera to work with me tomorrow so you can watch a bunch of these red-headed ants charge at me. It's a little scary, really.

Here are a couple of documents I found that outline F. Obscuripes behavior:

Territorial Behavior
Trail Laying Behavior
np category: ants


sideshow said:
Why would you lick the liquid on your finger??
December 05, 2007

jovial_cynic said:
For science!
December 05, 2007

Scott Johnson said:
They actually squirt the acid (formic acid) from their abdomens... if you disturb a nest you can watch them take a characteristic pose in which they raise up on their hind legs, bring the tip of their abdomen forward and squirt.
February 07, 2009

jovial_cynic said:
Scott Johnson -

You are correct. I learned some time after writing this post that they were not spitting, but rather squirting from their abdomen.

February 07, 2009

leroy said:
I was bitten by these little guys and went into shock. The allergy specialist said that we don't have venomous ants in W.A. and I think he is a nut.Was he george bushing me, or just an overpaid idiot?
May 24, 2011

jovial_cynic said:
leroy - the allergy specialist is correct. Also, ants don't "bite" to inject their poison. Fire ants, for example, have stingers... similar to bees.

If you were bitten by a formica obscuripes (red-headed ants in WA), nothing would have happened. Your reaction was likely from something else that happened at the same time. But it wasn't caused by the ants. These ants have no venom.

May 24, 2011

Lisa said:
The article you posted in regards to "territory" states the following: "For example, thatch ants (Formica obscuripes), the most dominant ant species in the Northern Hemisphere, protect their interests with stinging BITES and the release of formic acid from Dufour’s gland secretions which serves as both defense substance and alarm pheromones (Pomeratantz, M. 1972)."

So, do they bite, or don't they...?

February 19, 2012

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