Chocolate and Ants: An Experiment

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


100% Survival

(Vial 1)

70% Survival

(Vial 2)

77% Survival (10/13
Chocolate cereal-water

(Vial 1)

100% Survival
Chocolate cereal-water

(Vial 2)

100% Survival


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:


  • clean test tubes (I used six)
  • cotton balls (2 for each test tube)
  • water (tap is fine, just not softened)
  • a way to heat some of the water
  • paper towel
  • cocoa powder (for baking)
  • granulated sugar
  • cocoa cereal puffs
  • bowls or cups to mix ingredients in
  • measuring spoons and measuring cup
  • chop sticks (to tamp down the cotton balls and to stir the sugar-water)
  • paint brush – fine tip (for wrangling ants)
  • “pooter”(for wrangling ants) -see this post about how to make a pooter
  • access to a refrigerator (for wrangling ants)
  • funnel that fits in test tube (for wrangling ants)
  • tape
  • pen
  • source of ants, ideally with at least 60 ants


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:

  • sugar-water (the control)
  • sugar-water with cocoa powder added
  • cocoa-flavored cereal, with water offered as well

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.


  • preferably choose ants that don’t bite or sting
  • avoid areas that have been recently treated with pesticides
  • select ants from all the same colony, ants from different colonies are likely to fight

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.

Chocolate, Chocolate Products, and Ants

Recently a follower on our FaceBook page asked an interesting question,  “Will ants die if they eat chocolate?”

The question is an intriguing one. As many of you probably already know, consuming chocolate can be fatal to dogs and cats. A friend of mine recently had to rush her dog to the vet because he ate most of a large cake with chocolate in it.

The compound that is toxic to dogs and cats is an alkaloid called theobromine. Chocolate also contains small amounts of another, related alkaloid: caffeine. In fact, theobromine is a chemical precursor to making caffeine in plants. (Some of the older literature suggests chocolate does not contain caffeine, but newer, more sophisticated chemical tests have shown that caffeine is indeed present in chocolate). See the Hershey website for a discussion of theobromine and caffeine in chocolate.

Caffeine is known to kill insects. Nathanson (1984) suggested that it was a naturally occurring pesticide, and showed that it can inhibit growth in tomato hornworm larvae. More recently, scientists have been looking at genetically modifying tobacco plants to make caffeine. Their thinking is that the caffeine would repel or kill insects that feed on the tobacco. In their experiments, the caterpillars of the tobacco cutworm and small white avoided eating plants treated with caffeine. It was a repellent (Kim, et al.).

What about in ants?

As personal experience, I had once used a chocolate-covered peanut butter candy as a bait for some ants.

The sidewalk ants seem to prefer the peanut butter, although possibly a couple are trying the chocolate. It isn’t clear.

This fire ant also seems to be feeding on the peanut butter part. This highly-limited evidence might suggest ants might also be repelled by certain ingredients in chocolate.

Miyashira, et. al. recently looked at the effect of caffeine on leaf-cutter ants. They found that although there was “no conclusive effect” on the ants, the higher doses of caffeine did kill the mutualistic fungus that the ants use for food.

Back to our central question, can chocolate kill ants? Obviously caffeine can be a repellent and potentially have adverse effects on on insects. Caffeine is only a minor ingredient in chocolate, however. Chocolate is a conglomeration of some 300 different chemicals, any one of which could have an adverse effect on ants. Obviously more research needs to be done.

I was intrigued by this problem enough to set up a small experiment. I let you know more about that in an upcoming post.

What do you think? Do you know if chocolate has an effect on ants?


Kim YS, Uefuji H, Ogita S, Sano, H. (2006). Transgenic tobacco plants producing caffeine: a potential new strategy for insect pest control. Transgenic Res. 15(6):  667-72. (Abstract at PubMed) (Google the title for a free .pdf version)

Carlos H Miyashira, Daniel G Tanigushi, Adriana M Gugliotta, Déborah YAC Santos. (2012). Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus. Pest Management Science. 68 (6): 935–940.

Nathanson, James A. (1984). Caffeine and related methylxanthines: possible naturally occurring pesticides. Science 226: 184-187.

For more about chocolate and how it is made:

Ask-a-Scientist at Binghamton has general information about how chocolate is made

For more depth try The Science of Chocolate by S.T. Beckett (link goes to an excerpt at Google Books)