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On a recent trip to western New York State, we made a cool discovery.

Driving along a quiet country road, we came upon some huge ant mounds.

It's hard to tell how big they were until someone plays spokesmodel.

We found not just one mound, not just two mounds,

but more than twenty of them.

In the photo the size is a bit deceptive because the mounds were up on a bank along the road. However, they were still relatively massive. Most of them were at least two feet tall.

These impressive structures were the nests of the Allegheny mound ant, Formica exsectoides.

Each of the mounds was covered with many active ants. According to the literature, the colonies have multiple queens and split up via fission to form clumps of interconnected mounds.

The mounds are thought to help the ants regulate the temperature inside the nest, which in turn optimizes the development of the young.

Doing some comparisons, it looked like the top of each mound was clear of vegetation and the upper surface was relatively uniform.

This photograph shows a closer view of some ants working on top of the mound.

Lower down, the mound was covered with sparse vegetation and riddled with holes like a sponge. It would be fascinating to know whether these were for drainage, air circulation, or what.

Checking out the lower holes, we found they did serve as entrances and exits. One contained a myrmecophile, although it moved away so fast I couldn't tell if it was a beetle or roach nymph.

The ants were very active. It didn't take long to find a nearby foraging trail.


(This was filmed using a small endoscope attached to laptop, which required two people to run. I need to figure out a way to mount it on some sort of mobile tripod. Any suggestions?)

Compared to a similar-sized foraging trail of our Arizona Pogonomyrmex harvester ants, it was noticeable that these ants weren't carrying anything. Because they are known to feed on insects, as well as gather honeydew, they must process their food in the field. Anyone know more about their foraging behavior?

Even to people who aren't interested in ants, these mounds were such a presence that they inspired awe and curiosity. It would be great to get a chance to study them longer.

Have you ever encountered Allegheny mount ant nests?

Sometimes projects get interrupted, for example my attempt a few years ago to learn all the species of Pogonomyrmex harvester ants in Arizona. But just because there has been an interruption, doesn't mean the project will never be finished. Today let's take a look at the Maricopa harvester ant,  Pogonomyrmex  maricopa.

Pogonomyrmex-maricopa-227-crpped

Two things are apparent about these ants right away. The first is they are active at high temperatures. The day this photograph was taken the air temp reached a high of 104° F, and ants like Novomessor had disappeared into their nests by early morning. In contrast, these Maricopa harvesters were still going strong by mid-morning.

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The second thing that is apparent is Pogonomyrmex maricopa workers tend to hold their metasomas (gasters or rear sections) high in the air while walking or running. Pogonomyrmex californicus workers also do this. In this area P. californicus is quite distinct because the workers have dark metasomas and are found at lower elevations.  In other regions the colors and ranges overlap and the two species can be hard to tell apart. AntWiki has a quote from Cole's book about how to distinguish them.

By the way, the photographs for this post aren't the highest quality. That is because a prudent photographer keeps his or her distance from Pogonomyrmex  maricopa workers. Their most prominent claim to fame (or notoriety) is that Maricopa harvester ant workers produce the most toxic insect venom investigated so far (Meyer, 1996).

This species also has an unusual sting. The sting is barbed and can pull out of the ant's metasoma to be left behind within a mammalian victim pumping venom like a honey bee sting does.  It is best to give them plenty of space, although of course Alex Wild has a nice close-up shot.

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Harvester ants are known for collecting seeds from plants, but it is always interesting to look at what the ants have discarded in their middens. As well as various seeds, this midden has the exoskeletons of isopods. The needles and eucalyptus leaves are from nearby trees.

Pogonomyrmex-maricopa-midden-a-288In addition to more isopod exoskeletons, other piles had seed husks, beetle elytra and a few feathers.

harvesters-Pogonomyrmex-maricopa

Although they don't make a big mound of pebbles around their nest like some other desert ants, Maricopa harvester ants have been found to bring calcium carbonate to the surface causing a "cement cap" to form, which stabilizes the area around the nest entrance in sandy areas (Whitford 2003). Sounds like some interesting chemistry going on.

Pogonomyrmex  maricopa is a common and intriguing species of harvester ants. Hopefully we will learn more about them soon.

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According to Antweb, there are 15 species of Pogonomyrmex in Arizona (links go to Wild About Ants posts as they are added):

  • Pogonomyrmex anergismus
  • Pogonomyrmex  apache
  • Pogonomyrmex barbatus
  • Pogonomyrmex bicolor
  • Pogonomyrmex californicus
  • Pogonomyrmex (occidentalis-group) colei
  • Pogonomyrmex  desertorum
  • Pogonomyrmex hoelldobleri
  • Pogonomyrmex huachucanus
  • Pogonomyrmex (Ephebomyrmex) imberbiculus
  • Pogonomyrmex (californicus-group) magnacanthus
  • Pogonomyrmex  maricopa
  • Pogonomyrmex  occidentalis
  • Pogonomyrmex pima
  • Pogonomyrmex  rugosus

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After visiting the Desert Botanical Garden the other day, I was struck by a question of diversity. Of course there is a diversity of plants at a botanical garden. I certainly saw a number of different species of birds (including a great horned owl) and a bevy of different butterflies. There were squirrels, lizards and a ring-necked snake. What about ants?

Paratrechina longicornis-084Ants were visiting the extrafloral nectaries of the wild sunflowers.

Paratrechina longicornis-210-cactusThere were ants on the barrel cacti, probably also attracted to extrafloral nectaries.

Paratrechina longicornis-285In addition, ants were visiting the floral nectaries of the rush milkweed.

Paratrechina-longicornis-rush-milkweedThroughout the garden there was one species of ant, which is readily recognized by its extra long and thin antennae, as well as long legs. The species is Paratrechina longicornis.

Although it is often called the "crazy ant," I think a better name for Paratrechina longicornis is the longhorn ant. After all, many different groups of ants are commonly called crazy ants, including Dorymyrmex insanus, so that name doesn't help with taxonomy.  Also, the "crazy" behavior is somewhat subjective, but the extra long antennae are easy to recognize. The species name, longicornis, comes from the Latin words for long and horn. What do you think?

Apparently native to Africa, the longhorn ant has spread throughout the world, and is often found indoors even where it can't survive outdoors (see the map of its distribution at Antmap.org).

Longhorn ants are known to live in the soil of potted plants, which is probably how they reached the garden. They are also notorious for outcompeting other ant species in many settings, which probably explains why they are so prevalent.

The photographs show that the ants collect nectar from plants, but they are truly omnivores. They will feed opportunistically on seeds, other insects, and any foods we eat.

This short video by Helen McCreery shows Paratrechina longicornis workers engaging in group transport of a cricket. Cool!

 

Have you ever seen longhorn ants? Have you seen them cooperatively transport food?

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.

solenopsis-workers-during-swarm

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.

solenopsis-male-beginning-to-take-off-039

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.