Megan Hanson and partner

Willow Creek Middle School
Rochester, MN

Abstract

We wanted to find out if the size of the container affected the size of monarch larvae or adults.  We found four "critter cages" that were exactly identical except for size: small, medium, large, and extra large.  We put 10 first instar larvae in each cage and kept all other variables constant.  We weighed them every day.  When they became adults, we weighed them and measured their wingspan.  The smallest container produced the heaviest larvae and the largest container produced the lightest larvae.  Also, the ones in the smallest container pupated faster and came out of their chrysalides sooner. 

Observation

We know that for many living things their size is dependent on their container.
Examples:

• Keeping plants in small containers generally causes them to remain small.
• Keeping goldfish in a small aquarium will cause them to stay small; if they are put in a larger pond, they will get larger.

We thought that it would be possible for the size of the container to affect the size of monarchs as well.

Question

Does the size of the container affect larval size or adult size?

Hypotheses

Our class made several hypotheses:

• H₀ (null hypothesis):  The size of the container will have no effect on the larval or adult size.
• H_A1:  The bigger the box, the bigger the larvae and adults...and the reverse.
• H_A2:  The smaller the container the larger the butterfly.

Experiment

We found four "critter cages" that were identical except for size: small, medium, large, and extra large.  We put ten first instar larvae in each cage.

All larvae were fed the same number of frozen milkweed leaves (Asclepias syriaca) daily.  Each day we cleaned out every container and placed a wet paper towel in the bottom.  We kept all other variables constant. 

We weighed them everyday.  As soon as the first larva hung as a "J", we stopped weighing the larvae in that container.  When they became adults, we weighed them, tested them for parasites, measured their wingspan, and released them in the live butterfly tent that we have in our classroom.

Conclusion

We found out many things although our H₀ and H_A1 did not prove to be true.  H_A2 proved the most correct.

1. The larvae in the smallest tub went through their life cycle much faster (5-6 days difference between smallest and largest tubs).
2. Larvae raised in the smallest tub resulted in the heaviest butterflies; larvae raised in the largest tubs resulted in the lightest butterflies.
3. Larvae in the smallest tubs resulted in butterflies with the longest wingspan; larvae in the largest tubs resulted in butterflies with the shortest wingspan.

We think that, perhaps, the larvae in the large container had more room to move around and used up their fat supply.  Also, the frozen milkweed in the large container had more space to dry out than in the smaller tubs (so it was not as good to eat).

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