Fly Life: Fruit flies in the science classroom

Do you remember sitting in the science classroom in grade school, looking at pictures of pea plants to learn about inheritance? What if you could have tested Gregor Mendel’s theories of inheritance yourself (without watching plants grow)?

Well, you can! As it turns out, fruit flies are a great teaching resource for the science classroom. They are cheap, easy to maintain and store, and are well-understood, since they’ve been studied by researchers for over a century. These characteristics allow teachers to set up hands-on experiments for their students, and quickly adapt to students’ curiosity-driven questions.

Fruit flies can be used for teaching a variety of scientific concepts, from genetics to behavior, and the related experiments can be engaging, fun, and easy to understand. I want to talk about some of my favorite examples (some of which have gone from science fair projects to published peer-reviewed articles!).

Inheritance and Evolution

An example of a punnet square for mating a white-eyed and red-eyed fly. The white eye is caused by a sex-linked recessive genetic mutation. Male offspring have white eyes because they only have one copy of the gene (the mutation) from the white-eyed “mother”, while female offspring have a backup normal “red” copy inherited from the “father”.

Do you remember doing the punnet squares for Mendel’s pea plants? Punnet squares are diagrams used to predict what traits offspring will inherit from two different parents, and is the most common way to teach inheritance in the classroom. Fruit flies, with their short lifespan and quick generation time (offspring are available in only two weeks!), are perfect for a hands-on version of this experiment. Flies with different traits (such as red eyes and white eyes, or curly wings and straight wings) can be mated. While waiting for the next generation, students can predict what percentage of the offspring will have each trait. Two weeks later, they can sort the flies to test their predictions.

UNC’s The Wonderful Fruit Fly website is great for seeing how punnet square experiments can be performed with fruit flies.

The fly on the top has a mutation that causes white eyes. The fly on the bottom has normal red eyes. source

Another great example for an experiment was described in an article published in the journal Evolution. Because multiple generations of fruit flies can be studied in a matter of months, students can actually see evolution “in action”. In the published example, students added a single red-eyed fly to a large population of white-eyed flies. Flies with white eyes have poor eyesight and are less healthy than flies with red eyes. Over the course of the experiment, students watched as the healthier red-eye gene spread through the population, simulating the way a random advantageous mutation in nature can spread via natural selection.

This is only a couple of the dozens of interesting genetic experiments that can be performed in class. For more examples, the Tree of Life web project site is a great resource. 

Behavior and Health

Flies that eat dyed food have colored abdomens. Image modified from Isono and Morita, 2010.

Although fruit flies are most commonly associated with genetics experiments, they can also be used for behavioral experiments. One of my favorite examples is testing flies for food preference, in which students can give a group of flies a choice between two or more food sources, and count the number of flies that land on each. To make it even more interesting, the food can be dyed different colors. Once ingested, the dye is visible through the flies’ abdomens, allowing students to count how many flies have chosen each food based on color. Wouldn’t it be cool to see blue and purple flies under a microscope?!

Food preference experiments from middle school science fairs have actually made the news a couple of times over the past two years. In 2013, student Ria Chhabra developed an experiment to test whether organic food really is better than conventional food. She raised flies on each type, and found that flies raised with organic foods lived longer and healthier lives. The results were published in the peer-reviewed scientific journal PLoS One.

A similar story was released in 2014, when student Simon Kaschock-Marenda wondered whether fruit flies would like artificial sweeteners as much as normal sugar. He raised flies on sugar and several different sweeteners, including Truvia. His results, also published in PLoS One, showed that erythritol, the main ingredient of Truvia, was actually toxic to fruit flies.

These two heartwarming stories demonstrate how fruit flies can be used in the classroom to inspire students to pursue curiosity-driven science.

Want to start using flies in your classroom? There are many resources available online for experiment ideas, as well as “How-to” guides for setting up and maintaining a fly lab. One of the most comprehensive is the “How-to Fly Manual” from the researchers at the University of Manchester’s Fly Facility.  Another great resource is the “Drosophila Melanogaster in the classroom” blog, which details how to set up a classroom using fruit flies.  

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Many thanks to my friend Brittney for her help with resources and ideas for this post, gathered from her own volunteer experiences teaching fruit fly science to eager young minds.

I would also like to thank Dr. Andreas Prokop at the University of Manchester for some of the resources and inspiration for this post.  He and other fly researchers at the University of Manchester maintain an impressive array of lay information about fruit fly research and resources on their website (not just about how flies can be used in the classroom, but also how flies can be used to conduct high-quality research in disadvantaged regions and countries, where resources and funds may be limited).