LIFE CYCLE OF Pieris Rapae

INTRODUCTION

Behavior is the sum of the responses of an organism to internal and external stimuli. Ethology is the study of animal behavior in the context of evolution, ecology, social organization, and sensory abilities of an animal. There are two basic categories of behavior: learned and innate (inherited) behavior.  Experimental evidence suggests that the basis of both lies in the interaction between the animal’s genes and it's environment. This interaction influences how genes are expressed and regulated as well as generating long term effects in a species if differential selection forces are present. As with all genetically controlled features of an organism, behavior is subject to evolutionary adaptation.  As you study animal behavior in this lab, think in terms of both proximate causes, the immediate physiological events that led to the behavior, and ultimate causes, the adaptive value of the behavior (Morgan & Carter, 2002).

Feeding is arguably one of the most important of all animal behaviors.  We will investigate feeding behaviors of the larva (caterpillar) of the Cabbage White Butterfly (Pieris rapae). While the larvae are infamous as a worldwide pest of brassica crops (such as cabbage, broccoli, and canola), the cream-colored butterflies are important pollinators of many plants (www.fastplants.org).  During this activity, our goal will be to determine if the caterpillars have a preferred food and what factors might be influencing their “choice”. 

METHODS

Overview:

• Discuss/define "behavior" - (see Langton's Ant)
  
• Observe caterpillars and butterflies.
• Summarize observations - what is known?...what is unknown?
  
• Devise experiments to test the summaries.
• In behavioral arenas, set up a choice test between three food options.
• Place 3 foods equidistance around the perimeter of the arena.
• Place a single larva in the center of the arena.
• Observe, time and take notes on the activities and movements of the larva
• Repeat as many trials as time allows
• Revise summary based on experimental results

PROCEDURES

1. Clean and dry a glass bowl provided in lab.
2. Obtain one piece of each food type supplied and place them equidistance around the perimeter of the arena.
3. Obtain a larva and place in the center of the arena and note its sex.
4. Observe, time and take notes on the activities and movements of the larva.  We will pool all the data to obtain a frequency of larval visits to each food type.
5. When the larva has moved to a food and begun eating or stayed for three minutes, start a new trial at step one, but change the placements of the foods and the position of the larva (i.e., change the direction the head is facing when placed in the arena).
6. If time allows alter the experiment to test a new question that arose from your initial observations.  What is the stimulus?...color? …odor?
7. Conduct a Chi-Squared test of significance on pooled, class data. Your lab instructor will guide you through this at the end of lab.

                                                                                                                                        
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