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This week we're going to be doing a little trash talking. About ant trash, that is.

midden-veterans-oasis-rugosus-nov-2012

Ant trash or "middens" are the discarded materials that ants pile around or near their nests or mounds. Today we're picking through the middens of a colony of Pogonomyrmex rugosus harvester ants found at Veteran's Oasis park in Chandler, AZ. This first photo was taken on November 29, 2012.

What do you see? Small bits of rocks, of course. Those are common around harvester ant nests.

Being familiar with the plants found in the area, it is also possible to pick out some discarded seed materials.

The fuzzy strips are from creosote bush seeds. (Links go to posts about the plant at Growing with Science blog.)

creosote-bush-seeds(Creosote bush seeds)

You can also find some desert mallow, Sphaeralcea sp.

desert-mallow-seeds

The desert mallow seeds have a covering that is often seen in these middens.

desert-mallow-actual-seedsThis is what the desert mallow seeds look like with the covering removed.

Finally, the larger pale seed toward the upper right is a mesquite of some sort.

rugosus-midden-may-2013-074The next two photographs were taken on May 6, 2013.

rugosus-midden-may-2013-close_0089

Taking a closer look, it is apparent that for the most part these middens consist of discarded dark gray fringed seeds from brittlebush, Encelia farinosa.

brittlebush-seedsBrittlebush seeds

 

rugosus-middens-august-029

In August 2014, although there were still brittlebush seeds, the mix was more varied.

rugosus-middens-august-27

The larger, ovoid brown seeds are apparently from a honey mesquite.

honey-mesquite-seedHoney mesquite seeds

 

p-rugosus-entrance-close-111

Over the weekend I visited the same colony again (April 26, 2015).

See the brittlebush and desert mallow seeds near the top of the photograph? Some of those were being dropped by workers from outside the nest and picked up by other workers to be taken inside. Other were being taken out.

rugosus-middens-spring-0074Around the nest, the ground is covered with plant material likely deposited by the ants.

rugosus-middens-spring-2015-0073Note:  the brown round objects are jackrabbit scats, probably incidental.

rugosus-middens-spring-2015-closeClose-up, it looks like quite a few desert mallow, creosote bush and some brittlebush discards.

What does studying middens tell us?

First of all, from the photographs we can safely say that as the colony has matured it seems to be gathering a substantially larger amount of plant material. The amount of middens probably isn't a clear indicator of colony size, however, because the quantity of middens likely also varies with season, habitat, and recent weather. Taber (1998) indicates that worker harvester ants may store trash in underground chambers. These trash chambers may be closed off, or periodically cleaned out and brought to the surface causing a flush of discarded materials.

We can also make some assumptions about what seeds the harvesters are gathering throughout the season.  Thus, these Pogonomyrmex rugosus workers are gathering seeds from mostly local desert species of plants.

What ends up in the trash, however, may not accurately entirely reflect what is being consumed. It is likely some seeds are used completely and have no husks to discard. Think about it, how accurately does your trash reflect what you eat?

Have you studied ant middens? What did you find out?

Most of the time it doesn't look like much is going on in the Sonoran desert during the day.

desert-scene

Of course, looks are deceiving, because there is often a lot going on that is subtle.

After a rain like we had this weekend, however, life comes bursting out.

We went for a hike at South Mountain Park on Sunday morning. Rain had fallen in the night, and as you can tell from these photographs, it was still cloudy. It was also extremely humid.

messor-pergandei-mound-activity

 

It is impossible to capture the level of activity in photographs, but ants were just streaming out of their nests. These are shiny black Messor pergandei.

Rain stimulates activity for at least two reasons.

nest-messor-pergandei-good

First of all, the ants are scurrying to collect seeds.

messor-pergandei-carrying-seeds

Some desert plants release their seeds in response to rain. Also, the rain knocks down seeds that are higher up in trees and shrubs. That means there is a flush of new seeds to collect after a storm.

Most of you probably already know the second reason ants are hyper-active after a summer rain.

p-rugosus-princess-1.JPG

See if you can spot the reason in these photographs of a Pogonomyrmex rugosus nest entrance.

p-rugosus-princess-2.JPG p-rugosus-princess-3.JPG p-rugosus-princess-4.JPG p-rugosus-princess-5.JPG

 

Did you spot the princess (alate)?

She went back inside this time, but I bet later in the afternoon the alates from this nest were swarming.

Wish I had all day to watch them and a HD video camera. Maybe someday soon...

Are the ants swarming where you live?

 

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I always like to see what ants are collecting during foraging trips.

Sometimes it isn't easy to identify.

Tree resin? Hard candy?

What do you think it is?

And no, I didn't have the opportunity to collect it and see.

These Pogonomyrmex rugosus ants have found a pretty strange place to nest.

This is a hole in the asphalt of a parking lot.

Yes, this is their nest site.

Maybe they chose it for the view.