University of Minnesota

Will Monarch Caterpillars Eat More in the Light Than Those in the Dark?

Luke Salscheider and Christine Johnson
St. Francis - St. James United School
St. Paul, MN


Our study group did its work feeding monarch caterpillars in the light and dark. We wanted to determine whether monarch caterpillars would eat more in the light than those in the dark. The data below will help you understand how we performed the study.


We began with 88 first and second instar caterpillars. We split them into two groups. There were 48 caterpillars in the dark and 40 caterpillars in the light. We carefully traced the milkweed leaves onto a piece of paper, on this paper were squares each measuring 1 cm2. The reason we did this was to determine how much each group ate. We recorded this information for a week and 4 days.


Our figures are not perfectly accurate because we did not keep track of each caterpillar separately, nor could we account for portions of leaves that dried up. In addition to this, some of the larvae died. So, we counted the remainder of the caterpillars and found we had 34 in the light and 25 in the dark left. We performed the experiment by keeping track of how much milkweed the caterpillars in the light and in the dark ate in cm2. After they were all in the pupa stage, we calculated how much the caterpillars in the groups had eaten. The caterpillars in the light ate a total of 4687 cm2 and the caterpillars in the dark ate a total of 4287 cm2. We then divided these numbers by the respective number of caterpillars to get our final data.

(Photo: Luke Salscheider and Christine Johnson)
(Photo: Luke Salscheider and Christine Johnson)

This experiment was exciting but difficult. It took an amount of patience and work, but it was worth it. Some of the data we have we were able to find because our group worked well together. This was a very good experience for all of us and we learned many things about monarch butterflies. We learned that they eat more milkweed than we ever expected and their size does not affect their gender.

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