Teacher Notes

Fruit Fly Behavior

Inquiry Lab Kit for AP® Biology

Materials Included In Kit

Choice chamber tubes, 12" long, 8
Cotton balls, 100
Dissection pins, 25
Foam plugs, 35–44 mm diameter, 45

Additional Materials Required

Ethyl alcohol*
Drosophila melanogaster, 8 culture vials
Peanut butter*
Salad dressing*
*Examples of suitable materials for student-designed experiments

Prelab Preparation

  1. Obtain necessary items to be tested based on student-designed experimental procedures.
  2. Any laboratory chemicals requested such as HCl or NaOH should be no more concentrated than 0.1 M.

Safety Precautions

Once food-grade items enter the laboratory they are considered chemicals and should not be consumed. Please observe safety considerations listed on the chemical label for any items students select in designing their own experiments. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Avoid contact of all chemicals with skin and eyes. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.


Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All food-grade items and Drosophila chambers can be disposed of in the regular trash. To dispose of the fruit flies anesthetize and transfer to a fly morgue.

Lab Hints

  • Enough materials are provided in this kit for 24 students working in groups of three or for eight groups of students.
  • This lab requires at least two 50-minute class periods. The baseline activity and experimental design of the inquiry portion can be completed in the first class. The inquiry activity may be completed in the second class. Additional class time may be necessary for some groups. Additional time outside of class is required to complete data tables and chi-square analysis.
  • When a new substance is added to the choice chamber, use a fresh foam plug so that none of the preceding substance remains. If the substance added is particularly strong, it is a good idea to transfer the flies to an empty vial and rinse and dry the behavior chamber before continuing the experiment to ensure results are not skewed.
  • Vestigial or apterous mutant Drosophila may also be used to limit the fruit flies mobility. However, the results can take longer as they do not fly.
  • You may wish to subculture fruit flies in additional vials upon arrival to increase your population size in the event any of the original cultures die.
  • Have different lab groups investigate different questions in Part 1 ac so when the class compiles their data they will have investigated several variables.

Teacher Tips

  • This laboratory activity can be done during the study of concepts pertaining to interactions, big idea 4, or to cellular processes, big idea 2, specifically the capture, use and storage of free energy.

Further Extensions

Alignment with the Curriculum Framework for AP® Biology

Enduring Understandings
2D1: Reinforce the concept that all biological systems from cells and organisms to populations, communities, and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
2E3: Timing and coordination of behavior are regulated by various mechanisms and are important to natural selection.
4A6: Interactions among living systems and with their environment result in the movement of matter and energy.
4B4: Interactions between and within populations influence patterns of species distribution and abundance.

Learning Objectives

  • The student is able to refine scientific models and questions about the effect of complex biotic and abiotic interactions on all biological systems from cells and organisms to populations, communities, and ecosystems (2D1 & SP 1.3 & 3.2).
  • The student is able to design a plan for collecting data to show that all biological systems (cells, organisms, populations, communities, and ecosystems) are affected by complex biotic and abiotic interactions (2D1 & SP 4.2 & 7.2).
  • The student is able to analyze data to identify possible patterns and relationships between a biotic and an abiotic factor and a biological system (cells, organisms, populations, communities, and ecosystems) (2D1 & SP 5.1).
  • The student is able to analyze data to support the claim that response to information and communication of information affect natural selection (2E3 & SP 5.1). 
  • The student is able to justify claims, using evidence, to describe how timing and coordination of behavioral events in organisms are regulated by several mechanisms (2E3 & SP 6.1).
  • The student is able to connect concepts in and across domains to predict how environmental factors affect response to information and change behavior (2E3 & SP 7.2).
  • The student is able to apply mathematical routines to quantities that describe interactions among living systems and their environment that result in movement of matter and energy (4A6 & SP 2.2). • The student is able to use visual representations to analyze situations or solve problems qualitatively to illustrate how interactions among living systems and with their environments result in the movement of matter and energy (4A6 & SP 1.4).
  • The student is able to predict the effects of a change of matter or energy availability on communities (4A6 & SP 6.4).
  • The student is able to use data analysis to refine observations and measurements regarding the effect of population interactions on patterns of species distribution and development (4B4 & SP 5.2).

Correlation to Next Generation Science Standards (NGSS)

Science & Engineering Practices

Asking questions and defining problems
Developing and using models
Planning and carrying out investigations
Analyzing and interpreting data
Using mathematics and computational thinking
Constructing explanations and designing solutions
Engaging in argument from evidence

Disciplinary Core Ideas

HS-LS1.A: Structure and Function
HS-LS1.B: Growth and Development of Organisms
HS-LS2.D: Social Interactions and Group Behavior

Crosscutting Concepts

Cause and effect
Systems and system models
Structure and function
Stability and change

Performance Expectations

HS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
HS-LS1-3. Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
HS-LS2-8. Evaluate evidence for the role of group behavior on individual and species’ chances to survive and reproduce

Answers to Prelab Questions

  1. Fruit flies tend to lay eggs on fruit that is not yet ripe. This is an example of behavior that has been naturally selected to improve the survival of offspring. Why is it they might choose unripe fruit?

    Fruit flies choose unripe fruit because once the fruit starts to rot it will lead to bacterial and fungal growth or increase the likelihood it will be consumed by miscellaneous scavengers. Their offspring are more likely to survive and propagate the species if adults lay their eggs on unripe fruit.

  2. Fruit fly media is susceptible to bacterial and fungal infestation. Why?

    Fruit flies prefer moist conditions as discussed in the background section. These conditions are also ideal for the growth of bacteria and fungi.

Answers to Questions

Part A. Baseline Activity

When the flies are placed in a behavior chamber they are somewhat scattered. Once the chamber is positioned upright the flies tend to crawl upwards. When the chamber is inverted the flies will change direction and start crawling towards the original bottom which is now on top. There were no chemicals used in this activity so it is not a chemotactic response. Light was fairly equal around the tube so it was not a phototactic response. The only stimulus that changed was gravity indicating a geotactic response.

Part B. Exploring Inquiry

Students will test a variety of substances. Sample data for the variables tested by Flinn Scientific are shown below.



Flinn Drosophila Guide; Flinn Scientific, Batavia, IL; 2000; pp 1–11.

Student Pages

Fruit Fly Behavior


Drosophila melanogaster, also known as the fruit fly, has been studied by scientists for just over 100 years. Now it’s your turn to study not their genetics, but their behavior. What environmental factors trigger a fruit fly response?


  • Geotaxis
  • Chemotaxis
  • Phototaxis


The fruit fly can be found throughout the world and feeds on ripe or rotten fruit and the fungi growing on rotting fruit. Despite Drosophila’s small size, fruit fly studies have enlightened many areas of scientific understanding. Drosophila exhibit many interesting physical and behavioral characteristics. Its genome has been sequenced, its physical characteristics have been documented and mutated, and its behavior has been well chronicled. Because of all of their scientific applications, Drosophila are considered a model organism for geneticists and behaviorists.

Drosophila obtained its name based on observations of its characteristics. Fruit flies follow circadian rhythms that include sleeping in the dark and emerging as adults from pupa in the early morning. The latter behavior gave rise to the name Drosophila, which means “lover of dew.” The explanation for the species name melanogaster is based on physical features—Drosophila have a black abdominal area.

Physical Characterization
Like all insects, Drosophila have three main body parts—the head, the thorax and the abdomen (see Figure 1). The major structures on the head of a wild-type fruit fly are the large red compound eyes, the olfactory antennae, and the mouth. Between the eyes are two antennae the fly uses to sense odors. The mouth is a proboscis—the fly lowers it to suck up food like a vacuum cleaner. The thorax has six legs, two wings and, on the dorsal (top) side, a number of long dark bristles.

Sexing Flies
Identification of sex is most reliably done by examination of the genital organs with the aid of magnification. The external reproductive organs of both the male and female are located on the ventral-posterior part of the abdomen. The male genetalia are surrounded by heavy, dark bristles which are not present on the female (see Figure 2, Part A). This characteristic is quite distinct even in a fly that has just emerged from the puparium.

As flies age, the posterior portion of the abdomen becomes very dark in males and considerably lighter in females. The tip of the abdomen is rounded in males and more pointed in females. Generally, male fruit flies tend to be smaller than females but this is not a reliable characteristic to sort the sexes. Females have stripes on every segment of their abdomen. Males have shorter abdomens, and the last few segments of the abdomen are solid black. Males also have a set of brown anal plates on the ventral (bottom) side of the abdomen.

The front legs can also be used to distinguish sexes. There are sex combs on the front legs of the male fly (see Figure 2).
{11139_Background_Figure_2_Dorsal and ventral views of Drosophila}
Transferring Flies between Vials or Culture Tubes
Sometimes it becomes necessary to transfer flies from one vial to another. Reasons can vary from moldy media to simply wanting to increase stock. To transfer flies from one vial to another, first tap the vial containing the flies down so that the adults are gathered near the bottom. Quickly remove the foam stopper and invert the tube on top of the second vial containing fresh media. Note: A funnel may be placed in the receiving vial to reduce chances of the flies escaping. Tap the vials on the table so that the flies fall into the new vial and then quickly stopper the vial (see Figure 3).
{11139_Background_Figure_3_Transferring fruit flies from one vial to another}
Behavior Terminology
A taxis (from Greek, meaning to arrange) is an automatic, oriented movement towards or away from a stimulus. Animals move in response to a variety of stimuli. A chemotaxis is the movement in response to a chemical stimulus. The organism may move towards or away from the stimulus. Think about how an organism benefits by responding to chemicals differently in their environment. Phototaxis is a photactic response to light. A geotactic response is a movement in response to gravity.

Experiment Overview

Determine fruit fly behavior and preferences for certain environmental factors over others by giving them options within a choice chamber.


Choice chamber tube
Cotton balls, 6
Dissection pins, 2
Drosophila melanogaster, 30–40
Foam plugs for choice chamber, 35–44 mm diameter
Permanent marker

Prelab Questions

  1. Fruit flies tend to lay eggs on fruit that is not yet ripe. This is an example of behavior that has been naturally selected to improve the survival of offspring. Why is it they might choose unripe fruit?
  2. Fruit fly media is susceptible to bacterial and fungal infestation. Why?

Safety Precautions

Once food-grade items enter the laboratory they are considered chemicals and should not be consumed. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.


Preparation of the “Choice Chamber”

  1. Using a ruler, determine the distance half-way across the transparent plastic cylinder, approximately 6" from the end.
  2. Using a permanent marker, draw a line at the this halfway point as shown in Figure 4.
  3. Label one side of the chamber “A” and the other side “B.”
  4. To test different substances place 5 drops of water on a cotton ball. Add the solution being tested to the cotton ball. Note: Do not add so much solution that it drips down the side of the choice chamber.
  5. Insert a dissection pin through the center of the cotton ball.
  6. Attach the cotton ball to the foam plug as shown in Figure 5. Note: Solid pieces of fruit or other food may be attached directly to the foam plug with a dissection pin.
Part A. Baseline Activity
  1. Using the transferring procedure described in the Background section, carefully transfer 10–20 fruit flies into the behavior chamber.
  2. Hold the behavior chamber vertically. Which direction are the fruit flies traveling?
  3. Turn the chamber over and wait 30 seconds. Observe the flies again and note their direction of travel.
Part B. Opportunities for Inquiry

In this portion of the activity you will investigate fruit fly movement using a choice chamber that exposes fruit flies to different substances. Flies are very common in households. What types of foods or condiments found in households might attract or repel the fruit fly? Design an investigation to determine commonalities in substances that attract and repel fruit flies, their reaction to light and gravity. Directions for building the choice chamber are listed above.

Student Worksheet PDF


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