Kinds of Ants

When we first moved into our home, the yard was barren. Well, except for the numerous Solenopsis xyloni mounds.

Now, twenty years later, we no longer have Solenopsis xyloni. As the landscape has matured, the yellow Solenopsis amblychila have moved in instead. A few nights ago we noticed a swarming event just at sundown or about 6:00 p.m.

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The colony was under a small fairy duster plant next to a sidewalk. The workers were swarming about excitedly.

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The males came out first, like small airplanes getting lined up to take off.

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One by one, the males moved out onto the open sidewalk.

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In a blink of an eye, they were gone.

The princesses came out shortly later, when the light was too low for photographs.

It is unclear what triggered the ants to swarm. There hasn't been any rain in weeks. Perhaps it was the artificial rain of some nearby lawn sprinklers. Or perhaps it is simply because it is the end of the wildflower season and the fact that food, in the form of seeds, is wildly abundant.

No matter. It is always exciting to see ants swarming.

Now that the blog is all cleaned up, it is time to get out and spend more time looking for and watching ants.

dorymyrmex-insanus-firstThe very first colony I found turned out to be a common ant, but one that I haven't documented before. Do you recognize it?

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After checking a specimen under the scope, it was evident these were in the genus Dorymyrmex because there was a protruding bump on the propodeum, which gives them the name "cone" or "pyramid" ant.

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Here in Arizona, we regularly see another species in the same genus, Dorymyrmex bicolor, which has a brownish-red head and mesosoma.

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The dark-colored western cone ants are generally called Dorymyrmex insanus, although the scientific name has been changing "crazily" over a century, plus the genus seriously needs to be revised (Navajo Nature).

The common name isn't much better. As indicated by the "insane" species name, these ants are commonly called "crazy ants" because they move erratically. The name crazy ant causes confusion, however, because there are now invasive/pest species with similar names, such as Nylanderia fulva (the tawny or Rasberry crazy ant) or Paratrechina longicornis (the longhorn crazy ant). Perhaps we should stick to cone ants?

Dorymyrmex insanus are known to inhabit dry, open areas like the Sonoran desert. They live in small colonies (roughly 2000-3000 workers) in the soil. Like many other kinds of ants, they feed on scavenged insects/dead things and also tend aphids for honeydew.

In his book Adventures Among Ants (reviewed here), Mark Moffett noted that cone ants have been observed grooming harvester ants. Generally ants fight or avoid each other when they encounter ants of a different species, but these cone ants were photographed licking a much-larger Pogonomyrmex worker and leaving it unharmed. James Trager calls cone ants the "cleaner fishes" of the ant world. You can see his photograph at BugGuide.

Have you ever seen Dorymyrmex insanus ants? Where did you find them?

Reference:  Snelling, Roy R. 1995. Systematics of the Nearctic genus Dorymyrmex (Hymenoptera: Formicidae). Contributions in Science (Los Angeles) 454:1-14.  (Available as free .pdf)

4 Comments

In a recent trip to western New York, I noticed a trend. Whenever I found an ant colony (flipping rocks looking for bait for a family member who likes to fish)...

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an ant colony like these cornfield ants...

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I found thief ants.

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Everywhere.

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Take these Lasius.

 

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Can you see the thief ants?

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Let me give you clues. The thief ant is in the top right of first photo, near cluster of three larvae in second photo, and going into the tunnel just left of center in the last photograph.

Thief ants are named for their tendency to live with or near other ant colonies and then steal food from their "hosts."

They can also be found living in separate colonies.

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Some of the thief ant colonies I found living by themselves were quite large.

 

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Looks like quite a few new thief ants are on the way.

According to School of Ants, thief ants are distributed throughout the United States (although they don't show any records for New York State on the map). I had never noticed thief ants when I looked for ant colonies in that location in the past. I know my vision hasn't gotten any better, so that isn't it. It seems like thief ants have gotten a lot more numerous there.

Have you noticed more colonies of thief ants where you study ants? Do you think this a trend or a random happenstance?