Rover ant = Brachymyrmex patagonicus
On the Wild About Ants FaceBook page, Angela asked:
I am looking to answer a question for my daughter's daycare. They were doing a science experiment today and set out several kinds of cereal for the ants hoping to see which one they liked best. They set out Cheerios, Fruit Loops, Cocoa puffs (among others). When they came back to check a bunch of the ants had died. What would cause this? The daycare provider thought it was because of the cocoa puffs and that ants would die if they ate chocolate. So our first question is, will ants die if they eat chocolate?
This question reminded me of a Dave Barry column about his son's science fair project with ants. If you haven't read it and enjoy Dave Barry's sense of humor, I found a link (the column runs down the left side of the page.)
To answer the question, first of all worker ants do not actually eat solids, so they probably weren't breaking off pieces of cereal and consuming them. The worker ants would carry pieces back to the nest where the larvae would process them. It is unlikely that the ants would die on the spot (The questioner did reveal that pesticides had been used nearby.)
I did wonder whether the workers would be harmed if they consumed liquids containing chocolate. A quick search of the literature did not reveal much information about the effect of chocolate on ants, so I set up an experiment of sorts using rover ants as test subjects.
The results are as follows:
|Treatment||Percent Survival for One Week|
|77% Survival (10/13|
In this case the chocolate cereal didn't have an effect, but the ants presented with cocoa in the sugar water seemed to show some mortality. It is possible that the ants simply did not feed on the cereal, but they did not avoid it either. The water and the cereal were close and the ants stayed nearby.
The results suggest performing the trials again, perhaps with another ant species, might be worthwhile. What do you think?
~~~~Warning: The rest of this post is long ~~~~
If your child is thinking of doing a science project and wants to test this himself or herself, here's what I did:
1. Make a test tube ant nest to house the ants during the experiment. Prepare the test tubes by making sure they are clean. Fill each test tube 1/3 full with water. Push a cotton ball into each tube with a chop stick until it is about half way into the water. (The amount of cotton you will need is an art, so try it out beforehand). The idea is to create a humid, but not wet, chamber that will mimic a tunnel in an ant nest.
2. The "treatments" were:
Use the tape to label each test tube. If you have six tubes, then label two "sugar," two "cocoa," and two "cereal."
To start, heat the water or use hot tap water. The sugar and chocolate will mix with the water much quicker and easier if the water is hot, say about the temperature of a cup of coffee.
To create sugar-water that has a sugar content similar to that of nectar, add sugar to water in a 1:4 ratio. For example, add 1/8 cup of granulated sugar to 1/2 cup hot water. Mix thoroughly with a skewer or spoon until all the granules of sugar disappear into the water.
Now divide the sugar-water into 2 containers, about 1/4 cup in each. To the sugar-water in one container add 1 teaspoon of cocoa powder. Again, stir until mixed thoroughly. Allow to cool enough for ease of handling.
Soak two approximately one-inch-square pieces of paper towel in the sugar-water container. Remove and squeeze out the excess sugar-water, until they are about a wet as a damp sponge. Roll into a loose ball and add one to each of the test tubes labelled "sugar."
Soak another two one-inch-square pieces of paper towel in the sugar-water with cocoa powder added. Again, drain the excess cocoa-sugar-water and roll into a loose ball. Add one to each of the two test tubes labeled "cocoa."
For the final two test tubes, soak two approximately one-inch-square pieces of paper towel in water. Remove and squeeze out the excess sugar-water, until they are about a wet as a damp sponge. Roll into a loose ball and add one to each of the test tubes labelled "cereal." Add a piece of cereal to each of the test tubes, as well. (I used 1/2 a puff for each tube.)
3. Ant Wrangling
Locate ants. I wanted to use 10 ants per test tube, so I needed 60 ants.
I chose a "domestic" source of rover ants. These ants don't bite of sting, and are an introduced species that could be considered to be a pest. They occur in high numbers.
As you can see in this photograph, rover ants are also ridiculously small. I would recommend that you use larger ants, if available.
Create a cotton ball stopper for each test tube, and then set the stoppers aside.
Using a pooter, aspirate (suck up) 10 ants. Place the pooter with the ants in the fridge for at least five minutes to slow the ants down. In the mean time, place the plastic funnel in the opening of the test tube. Remove the pooter from the fridge and tap the vial sharply. Working quickly, remove the pooter cap and dump the vial into the funnel. Tap sharply. Having an assistant with a find paint brush to wrangle stragglers is helpful. As soon as the ants are in the vial, stopper the top with the cotton plug you prepared earlier.
Repeat until you have 10 ants in each vial.
Store in a quiet, warm place with dim natural lighting or darkness (avoid bright light). I checked the ants each day. After one week I counted the number alive and dead using a microscope.
I had a failure of the cotton plug in one of the control tubes, so that was lost. Good thing I made two.
All the chocolate treatments grew some mold, the sugar-water control did not. Note: always wash your hands and equipment carefully to prevent mold issues.
Please let me know if you have any questions or comments. If you do the experiment or a similar one, I would love to hear how it comes out.
Note: This post is not for the squeamish.
It all started when I noticed rover ants in a flower. It wasn't just any old flower, though.
Ever seen one of these?
Commonly called carrion flowers or African starfish flowers, plants in the Genus Stapelia are low-growing (only 8 to 12 inches high), succulent perennials. They mainly grow in southern Africa, but can are treated as an interesting potted plant elsewhere. You can see the plant in the background of the photograph below.
The Stapelia flower looks weird, doesn't? The surface is brick red, wrinkly and covered with soft hairs. It looks quite a bit like bloody mammal hide.
If you were standing with the photographer, you just might be holding your nose, too. The common name carrion flower comes from the foul odor the flowers produce.
The odor is a powerful attractant to blow flies and other types of carrion flies.
Why does the plant do this?
The answer is stuck to this poor fly's mouthparts. See the orange bundles? Those are the pollinia (it has two bundles). Pollinia are pouches that release pollen. The fly picks them up at one Stapelia flower and loses them at the next, pollinating the plant.
The flies are so taken in by the deception that, depending on the species, they lay eggs or larviposit (lay larvae) on the flower.
That is where the rover ants come in.
The rover ants have found a ready supply of protein in the form of fly larvae and eggs.
Ironically, the rovers have found real "meat" in a plant that is using a meaty appearance as a deception.
Other types of ants visit Stapelia flowers. In this video, you can see ants in some of the scenes.
For more in depth information about Stapelia and more photographs of ants in Stapelia flowers, see S.P. Bester's article from the South African National Herbarium