Friday, March 23, 2012

Ant Swarm

Everybody likes a good swarm and ants are master swarmers.  I believe this species is Acanthomyops interjectus, AKA Larger Yellow Ant, one of several that produces a lemony fragrance.  They nest behind the brick wall of our cellar and release thousands of winged queens around this time every year.  Usually the swarm takes wing in the basement, but this year’s warm weather may have altered their pattern to an outside departure. 
Workers are a yellow or copper color.  Other similar species share this appearance and identification comes down to things such as eye size, hair placement and body size.  I hope I was looking at the right things as I worked my way through the ant key.
Winged females stage beneath rocks and other cover or in shallow subterranean chambers.  When it comes time to leave the nest, the workers rapidly open passageways and shoo the fliers out of the nest.

The workers provide some protection during the exodus, but I think their primary function if to persuade the unfertilized Queens to get out and fly.  Workers are quite apt to give a laggard Queen a little bite of encouragement.

Once the Queens get moving, the action proceeds at a frantic pace.  The goal is to become airborne, mate and settle down somewhere to start a new colony.

The way they climb over one another, it’s a wonder any of them ever take off.  The literature identifies late summer as the breeding time for these ants.  Early spring swarms are described, but no winged males are reported.  I know that in all the years I’ve been watching this colony, I’ve never seen a spring time male.  So I’m puzzled as to what happens to all of these departing Queens if there are no males out there waiting.

After successfully mating, the Queen will shed her wings.  With no males in the vicinity, there could be no mating, but when the swarming activity began to reach its end, I noticed several wingless queens.  Most were wandering the ground in an apparent search for a secluded spot.  A few stuck with their winged colony members.  These may have disappeared back into the protective chambers with the Queens that didn’t make it into the air.  This swarm is in its fourth day with activity beginning about a half hour before sundown and ending about 20 minutes later.  The swarm suddenly erupts from the ground and at some silent signal, all the ants that haven’t flown are suddenly sucked back into their tunnels.

Not all of the hopeful Queens survive the flight.  Water is a death trap.  I frequently find winged Queen ants floating in the Water Garden.  When the flight originates only a few feet away, the number of floating ants really adds up.

The bounty isn’t wasted.  Just about everything likes to eat Queen ants.  Frogs cleaned up most of the swimming ants.  Water Striders also took advantage of the glut of food.  Apparently mating doesn’t interfere with eating, at least for the female.


  1. Very interesting post...thank you for the info.

  2. Great post - worthy of a Wilson (E.O.).

  3. Hi Steve-

    You know I love the ant posts! I concur with your ID, though most myrmecologists now call this ant Lasius interjectus. This species flies earlier than most in the genus, spring to early summer. Colonies of many ants tend to produce all or mostly only one gender of winged ones, so there are males around, but not brothers of the girls emerging from the nest you photographed.

    By the way, it's worth mentioning that the mated females of this species cannot found a colony alone as in most ants, but must invade a colony of another species in their genus, probably L. alienus in this case. Once in the host nest, if all goes well for her, the parasite queen kills the host queen, then becomes accepted by the workers, who then rear the parasite's brood, and eventually die off. This has only rarely been observed, perhaps because young colonies are quite difficult to find, and also because the turnover is relatively quick.

    As with your Formica exsectoides, I live just a touch too far south to have this one as part of the local fauna here, so, lovely to see these photos.

  4. Hi James. Thanks for the information. I use Gary Coovert's Ants of Ohio for my identification. He listed Lasius as a synonym.

    That's really interesting about the queen taking over the nest of other Lasius species. I can see how that would be a hard thing to witness.

  5. For a while, the Acanthomyops species were recognized as a genus, and Coovert's book came out during that period, before two separate recent phylogenetic studies found them nested nicely within Lasius. Of course, there is no objective criterion for what constitutes a genus, so one could just as well call all the subgenera, genera, but that's another discussion (and I'm glad no one has).

  6. Hi James. It seems that ever shifting taxonomy is a fact in all groups of life forms. Back when I was in school, I was taught that scientific nomenclature was important because it gave each living thing a single name, so there was never any confusion about what plant or animal was being discussed. It seems anymore that common names better serve that purpose.

  7. Steve, mine are flying right now and are very yellow! There are plenty of males in the mix also, so I am wondering if my ants are a different kind. These are emerging from several feet away from the house and I have never seen them before in my life. I live in northern Colorado. Any ideas what mine are?

  8. Hi Colleen. There are several similar species in this genus and some of those do live in Colorado. Yours may not be the same species as those I show here, but they probably look enough alike that you would need magnification to tell the difference.