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What Do Harvester Ants Eat?

Harvester ants are pretty gross. And I’ve seen them come in droves, which makes it even more disgusting. One key to prevention is knowing what they eat.

So what do harvester ants eat? Harvester ants prefer seeds close to their nests, but they can travel as far as 30 miles if needed. These ants favor a homogenous diet but their diet choices can expand when food supply starts dwindling. Besides seeds, they prefer vegetation. But they also eat dead insects when food is scarce.

Read on to find out what harvester ants eat, their peculiar food preferences and interesting foraging habits that you didn’t know about.

What seeds do harvester ants prefer?

As their name implies, harvester ants love foraging for vegetation with a strong preference for seeds. These ant species are hard working seed collectors. In certain environments, they are the main predators for seeds. An interesting question arises at this point. Do harvester ants have a preference for certain kinds of seeds?

Out of a blend of seeds, will they behave in the same way as kids do? As we all know, most kids pick out chocolate chips preferentially from a trail mix.

At the University of California, Riverside, researchers set out to investigate whether harvester ants have a stronger tendency for collecting seeds on the basis of availability or on the basis of seed species. This data will give useful information about which plant seeds have a higher chance of sprouting into a plant and which seed types are more likely to end up as meal in the ant nest.

These pressing questions on seed survival are important because foreign invasive plant species are proliferating rapidly in California and wreaking havoc on local plant species. The findings of these researchers were published in Environmental Entomology.

The research commenced with some rudimentary observations. What kinds of seeds were the ants foraging? Harvester ants normally go back and forth to their colony in the form of lines that are called trunk trails, which can be several meters long. These harvester ant trails are to be found in the areas that contain food for harvester ants. Such areas are referred to as foraging patches.

Lead researcher Christopher Biggs closely examined ants returning to the colony along the trunk trail and took note of the seeds that the ants were carrying back to the nest. He also made observations at foraging patches to find out more clues about their foraging behavior.

This scrutiny provided answers about the effect that harvester ants had on the seed bank. Seed bank refers to seeds lying on the soil surface. Briggs took a close look at the trunk trail, keeping his face about 30 cm away from the column of moving ants, which had no effect on the harvester ants.

However, the ants took strong note when he tried to obstruct their path with his foot. The pain from harvester ant sting was excruciating. Briggs likened the pain of harvester ant sting to a large screw being forced into the stung body part for several hours. Unfortunately, for human beings who get in their way, harvester ants have developed a painful venom as a defense against predators.

Daring entomologist Justin Schmidt has given a high pain rating to harvester ant sting. This sting scores 3 out of an index of four. It is even more painful than a wasp sting.

Thankfully, the results of the study vindicated the pain endured by Briggs. Much to their delight, researchers found that harvester ants have a deeper proclivity for certain invasive species seeds. This preference was largely unaffected by the availability of these seeds, implying that harvester ants are highly partial to these seeds. Harvester ants had a strong preference for Erodium cicutarium, which is also known as filaree.

In addition to filaree seeds, the ants were attracted to mustant seeds, which are another exotic plants species seed. The peculiar aspect of this foraging behavior was that it had no effect on the seed bank within the foraging patch.

The researchers then set out to test if harvester ants had a similar preference for other kinds of seed species. Researchers studied how these ants behaved with respect to a combination of mustard, filaree, buckwheat and brittlebush seeds. Brittlebush and buckwheat are local species, whereas filaree and mustard are exotic species. These seeds were presented to the ants in covered petri dishes that had small holes on the sides to admit ants and exclude birds and other animals at the same time.

The findings were intriguing. One colony had a greater predisposition for mustard, filaree and brittlebush seeds at the expense of buckwheat. On the other hand, another colony preferred filaree seeds over all other types. One common aspect of both scenarios was that ants are strongly predisposed to filaree seeds, despite the bristle-like exterior of these seeds, which adhered strongly to adjacent vegetation, thereby making it more difficult for ants to carry away these seeds.

Although the harvester ants foraged extensively for mustard and filaree seeds, this did not deplete the seed bank as the researchers were expecting. The authors speculated that part of the reason could be that the ants were abandoning the foraging site before the area was significantly depleted of seeds. Another reason for this phenomenon could be the plethora of seeds in the region.

Unfortunately, at this point, it appears that the presence of exotic seeds is an exotic addition to the menu of harvester ants and nothing more. Researchers failed to get the results that they were hoping to attain from harvester ants to control the exotic plant species population. Apparently, researchers will have to look towards other avenues to reduce the proliferation of exotic invasive plant varieties.

Foraging behavior

Harvester ants are known for their foraging behavior. They play an important role in wildlife since they help to disperse seeds. Harvester ants also eat seeds.

During the daytime, harvester ants forage grassy areas for seeds and other vegetation. They bring these things back to their nest for feeding the colony.

Harvester ants finding food in hot and dry conditions gradually lose water. However, they compensate for lost water by metabolizing fats from the seeds that they consume. The foraging activity of the colony follows a positive feedback pattern.

That is, when more ants carry back food to the colony, then more ants are sent to look for food. This is something that almost everyone observes at some point in time. Where a food source has been discovered, then these ants will swarm the location to carry back the food back to their nest.

Weather conditions play a major role in the behavior of harvester ant species. For instance, in hot and humid conditions, the Messor Andrei harvester ants are attracted to the food bait in higher numbers. The numbers increase with rising humidity. Food availability, as well as humidity, both depend heavily on weather conditions.

Food for harvester ants in the wild is distributed through flooding and wind. Rain exposes the seeds located in the upper crust of the soil.

In the Pogonomyrmex barbatus harvester ant species, differences in conditions like food availability and humidity have a strong influence on the daily foraging activities of all kinds of colonies.

The foraging behavior of colonies with respect to humidity may vary across colonies. Colonies differ in the frequency at which they forage during the year. In general, most colonies forage more during days of higher food availability and humidity. For instance, after rainfall, when the seeds are abundantly available. During very dry days, few colonies forage for food.

From this, it appears that harvester ant colonies weigh the potential costs between food availability and loss of water. There is also a difference between colonies with respect to the number of foragers that are sent out in response to incoming foragers. Most colonies have a tendency to strongly adjust the numbers of outgoing foragers in response to incoming foragers during good conditions. But during poor conditions, few colonies make such a marked adjustment.

Researchers have found that a returning forager harvester ant communicates with another inactive act so that it is stimulated to travel out of the nest in search of food. This interaction involves contact between antennae for a brief time span at the tunnel entrance. During this contact, the inactive ant deciphers the hydrocarbon profile and whether or not the returning ant is carrying food in order to determine its task.

A faster forager return rate may imply food availability nearby since the search duration is determined by the level of food abundance. When more food is available nearby, then a larger number of ants return with food and the foraging trips have shorter time spans.

These results have been ascertained from careful observations over a period of a few years. Researchers will have to do more work to determine why colonies show differences in foraging habits.

Related questions

Where do harvester ants live? Harvester ants reside in southwestern countries from the U.S., for example Utah, Texas, California, and Florida, largely in prairies and grasslands. The quantity and quality of food, hormones and temperature produced by employees and queen decide if it’s the female becomes a worker ant or a queen.

Can harvester ants kill you? A few, such as the Maricopa harvester ant, will kill you quickly by toxin. It only requires a couple of hundred bites with this particular ant into kill an individual (in comparison to 1,500 for honeybees, supposing you aren’t allergic). Also after one bites you, others will follow (they smell exactly the alarm pheromones from the sting), therefore death will be quick.

How do harvester ants reproduce? The fertilized females establish new colonies and eventually become queens. Throughout reddish harvester ant breeding swarms, winged females and males emerge from their colonies. They’re drawn to one another by pheromones. After mating, the mated females lose their wings and set new nesting sites.