ACTIVITY 21

Feeding Behavior Experiment*

Teaching Objectives:

1. Students will conduct experiments using proper scientific methods.
2. Students will observe that butterflies use their feet for tasting.

Materials Needed:

• Painted lady butterflies or suitable substitute; capture in the wild or order from Biological Supply Houses
• Sugar
• Distilled water
• Forceps or tweezers
• Zip-locking plastic bags for transporting the butterflies
• Petri dishes or saucers

Procedure:

Discuss with the students the fact that when house flies land or are placed on a surface of a food item such as a piece of fruit their sponging mouthparts (proboscis) extend to the food surface and feeding commences. This phenomenon occurs because house flies have chemoreceptors (taste buds) on their feet (tarsi) which allow them to "taste" their food before they extend their mouthparts.

Many insect species in the order lepidoptera (butterflies and moths) feed by extending their coiled proboscis and syphoning nectar and other nutrients. Do these insects taste with their feet?

Put for this hypothesis to the class: Painted lady butterflies will extend their proboscis when tarsi come in contact with an appropriate food item.

Mix sugar and distilled water for sugar solution. Try different concentrations to determine a threshold response.

• 1 cup water : 1 tablespoon sugar
• 1 cup water : 2 tablespoons sugar
• 1 cup water : 3 tablespoons sugar
• 1 cup water : 4 tablespoons sugar.

Take one butterfly which has not eaten for 12-24 hours and place it at the edge of the dish with the front tarsi (feet) sitting in the sugar solution. Using the forceps or tweezers, hold the butterfly by its wings until it commences feeding.

Observe the response of the adult. Does it immediately extend its proboscis? Does it wait and then extend? Does it not extend at all?

Try the same adult on different sugar solutions starting with the weakest. To see if there is a real pattern, try many different adults that have not fed for 12-24 hours.

THINGS TO CONSIDER: Once a painted lady has been fed it should not be fed again for another 12-24 hours if you wish to repeat the experiment with that individual.

Discussion:

Can we conclude that a painted lady tastes with its feet? How could we investigate this further?

Supplemental Activities:

Try distilled water. Do you get the same response?

Try saltwater. Do you get a response?

Try other insects.

Try blindfolding some students and having them stick their hands in salt water, sugar water, and plain water. Can they tell the difference? (This may be possible if a student has a cut on his or her finger.)

*Created by the Smithsonian Institution's National Museum of National History