University of Minnesota

Does Temperature Affect Pupae?

Matt Piehl and partner
McGuire Jr. High School
Lakeville, MN


Will a pupae put into a hot temperature (28 °C) emerge more quickly than a pupae put into a colder temperature (3 °C)?


Monarchs live in the northern regions of America, excluding Alaska, and parts of southern Canada in the warm summer months. When the weather turns colder in the fall as winter approaches, the adult monarch butterfly migrates south to Florida and Mexico. From this information, I found the average temperatures of both climates. They were right around 26 °C. This means that monarchs need warm temperatures to survive. My cold caterpillar will not survive because of the cold conditions.

When two pupae are put into two different temperatures, the pupa put into the warm temperature will emerge first. Most pupae emerge during the warm summer months, while the cold pupae will act as if in hibernation. Monarchs are most active in temperatures above 5 °C, so the cold pupa will not be active. The heat will act as incubation, just like a mother hen and her eggs. The warm pupa will emerge first because of the incubation and prime environmental conditions.


The materials that I needed for this experiment were four caterpillars in the fifth instar stage or in the "J" stage. I also needed four caterpillar boxes, refrigerator space, and heat box space the size of two caterpillar boxes. A thermometer was also needed to find the temperatures of each box.

Some things in my experiment never changed. These things are called the controls. When the caterpillars were in the fifth instar stage, I fed each of them two leaves. Another thing that never changed was the size of the boxes. Each box was exactly the same size. A third control was the amount of light each pupa received. All the pupae were kept in complete darkness. A fourth control was the person who measured the caterpillars/pupae. My partner always measured the cold pupae, and I always measured the hot pupae. Another control was that we never changed the caterpillars' diapers.

Every experiment has two variables. One is called the independent variable, the other is called the dependent variable. My independent variable is the temperature of the boxes. My dependent variable is the emerging rate of each pupae.


  1. Choose ten caterpillar boxes of exactly the same size from your teacher's collection in the science room.
  2. Put a "diaper" in each side of all the boxes. A diaper is made by dampening a paper towel. Then you put the damp paper towel in the bottom of the box.
  3. Label the boxes. Put some masking tape on the side and top of each box. Using a permanent marker, write your name and hour on the tape.
  4. After that, prepare a heat box. Plug in a heat pad and put a large box over the pad.
  5. From your teacher, get ten caterpillars in the fifth instar stage. Put one caterpillar in each box.
  6. Take a ruler and measure each caterpillar. Note these measurements in centimeters on a piece of paper.
  7. Take five of the boxes and place them in a refrigerator.
  8. Using a thermometer, measure the temperature of the refrigerator in degrees Celsius and record it.
  9. Place the other five boxes under the box on top of the heat pad..
  10. Using a thermometer, measure the temperature of the heat box in degrees Celsius and record it.

In this experiment, I chose ten caterpillars in the fifth instar stage. I put them in two different climates; five larvae in a cold climate (refrigerator), and five larvae in a hot climate (hot box). Everyday I observed them and noted the time when they emerged from their chrysalises. I did this to test whether or not temperature affected the emerging rate of pupae. I was hoping that the results from my experiment would explain why monarchs migrate.


(Photo: Matt Piehl and partner)

The results of my experiment were very decisive in my opinion. The larvae in the heat emerged faster than those in the cold. The larvae that I put into the refrigerator turned black and died. One of them was in the "J" shape, but he froze to death and fell from the top of the box. The larvae that were in the heat box pupated and emerged into the adult stage of metamorphosis very quickly. Monarchs need warmth to stay alive. This is because they are cold-blooded. Monarchs can be seen lying on a rock or another object in the sun soaking up the sun's rays. These butterflies are not active in temperatures below 4 °C , as proven in my experiment by the dead, cold caterpillars.


There were some uncertainties in this experiment, however. One of them was that other people could have mistreated my caterpillars. They could have taken them out of the cage and poked them, or other nasty deeds. I could interrogate the kids and ask them if they played with my caterpillars. Another uncertainty could be whether or not the cold caterpillars were sick and dying in the beginning. They could have had an unseen disease that killed them. I could do an autopsy on the dead caterpillars to see if they really did have a disease.

Every time I do this experiment, I think the results will be the same because monarchs are cold-blooded. My new test idea would be to put two caterpillars in room temperature and two caterpillars in a heat box. I would do the experiment in exactly the same way, only substituting room for the cold temperature. I want to discover with this new experiment whether or not a butterfly would survive in a slighty colder climate than summer in Minnesota and winter in Mexico. The hot pupae will emerge first, because of the incubation the heat gives to the pupae.

The most important thing I learned from this experiment was that monarch butterflies need to migrate to survive. They cannot live in regions that have temperatures below 4 °C everyday. I really liked doing this experiment, but I feel a little bit guilty about killing two larvae. My purpose was to test the effects of temperature on the emerging rate of pupae. Cold kills pupae, but hot speeds up the pupating process.

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