Objective
To investigate and detect the orientation of movement in houseflies in response to a light stimulus and to determine whether they exhibit positive or negative phototaxis.
Principle
Phototaxis is a type of tactic movement (orientation behavior) where an organism moves toward or away from a light source.
- Positive Phototaxis: Movement toward the light source.
- Negative Phototaxis: Movement away from the light source. Visual receptors (compound eyes) and nervous system of houseflies coordinates the locomotor organs to move the body toward the perceived stimulus.
Methodology
- Apparatus: A T-shaped or Y-shaped glass tube (T-maze), a light source (LED or incandescent bulb), black cloth or paper to create a dark environment, and several healthy houseflies.
- Setup: Cover one arm of T-maze with black paper completely, while the other arm is remained exposed to a controlled light source.
- Procedure:
- Place the houseflies at the base (entry point) of the T-maze.
- Ensure the environment is otherwise dark to prevent external light interference.
- Switch on the light source at the end of the “light arm.”
- Observe the direction of movement of each fly over a set period (e.g., 5–10 minutes).
- Record the number of flies that move toward the light, move into the dark, or remain stationary.
Result
- Observation: A significant majority of the houseflies (e.g., 90%) consistently moved toward the arm of the illuminated tube.
- Behavioral Pattern: The flies often showed rapid wing movement and direct crawling toward the highest intensity of light.
Conclusion
As they were moving towards light therefore we can conclude that houseflies exhibit positive phototaxis. This orientation behavior is an innate response that likely helps the flies in nature to find open spaces, food sources, or mates, as light often correlates with the outdoors and availability of resources.