University of Minnesota

The Effects of Magnets on Monarch Pupae

Chris Ramage
Willow Creek Middle School
Rochester, MN

Chris Ramage with his insect fair project display (Photo: Chris Ramage)


I watched the caterpillars and checked which direction they would "J". On the side of the containers I placed a powerful magnet. I did this to determine if the direction of the "J" was affected by magnetism. However, the direction of the "J" appears to be largely random. Only 19 caterpillars were tested, however; so if a larger number were checked, a definite pattern might emerge. My science teacher, Mrs. Cansler, performed a similar experiment with similar results. However, while I had a magnet attached to one side, her experiment consisted of two magnets, one above and one underneath the cage.

Two things I learned during the testing were that the bad taste of a monarch does not deter spiders (one got into one of the cages, which is why I only had 19 monarchs "J"). Also, that the size of a monarch is not always an indication of its age, as I had several smaller caterpillars "J" while the larger ones continued eating.

What is Magnetism?

Before discussing how magnetism affects monarchs, it is important to have a clear idea of what magnetism means. Simply put, magnetism is the attraction of one object to another. This applies to anything with any mass, including people (Note, however, that the magnetic field emitted by a human is very weak, due to the fact that humans are not magnetized and that there is very little metal in a normal human).

Although everything has a magnetic field, only metal can be magnetized. When an object is not magnetized, the charge it contains appears something like this diagram:

Unmagnetized (Photo: Chris Ramage)

When an object is magnetized, its electrons are aligned like this:

Magnetized (Photo: Chris Ramage)

An object has a charge when all of its electrons are aligned in the same direction. Also, this gives a magnet two poles, a north pole and a south pole. If one attempts to put two north poles or two south poles together, they will not connect. North is only attracted to south and vice versa.

It is possible to think of the earth as a giant magnet. The earth is made up of four layers: the crust, the thin strip of relatively cool land on which all life dwells; the mantle, a giant bed of molten rock and lava; the outer core, a layer of liquid iron and nickel; and the inner core, a giant ball of pure iron. The iron of the inner core is theorized to be packed in a tight hexagonal form. This would make it a very efficient magnet.

The Earth's Magnetism and Its Effect on Animals

The inner crust of the earth acts like a giant, supercharged magnet. However, the magnetic fields do not simply emanate out from the earth. If one were to take a globe and look around the northernmost Canadian islands, there is a spot, often marked with a red X, that is labeled as the North Magnetic Pole. From this point comes a extremely dense field of magnetically charged particles, which form, along with the Southern Magnetic Pole located in Antarctica, the Earth's magnetic field (The explorer Roald Amundsen spent two years trying to determine the exact location of Magnetic North, only to discover that the area it covers moves in a broad circle about twenty miles around).

Many animals seem to use the magnetic poles to help them find their way to and from nesting sites. Homing pigeons, for example, can find their way back to their roost even if taken hundreds of miles away, even if they were asleep while being transported, or even if blindfolded. Yet they immediately become disoriented if magnets are hung from their necks. This seems to indicate use of the magnetic poles to find their way home. Recently, in France, a scientist decided to test whether children could find their way home without using their senses. He blindfolded a group of schoolchildren and took them out into the country, away from civilization or any other recognizable landmarks. He then removed the blindfolds, and asked them to point towards their houses. Most pointed in the correct direction. Again, magnetism may be at work.

Monarch butterflies regularly fly up through America, breed, lay their eggs, and go down to a small group of trees in Mexico to roost. They always go to the same trees and it is a mystery how they are able to pinpoint the exact roosting spot, especially since those butterflies have never been there in their 2-8 month lifespan. Once more, magnetism seems to be the key. My project, therefore, was concerned with whether the direction in which a monarch butterfly pupates has anything to do with magnetism.


The first question I asked was how do monarchs find their way to the trees in Mexico. After doing research and discovering that it is likely that they have natural "compasses" in their brains, I began to wonder if this was the only time that monarchs would use these abilities. So I began thinking about what other uses a built-in compass might have. My experiment tries to determine whether magnetism affects what direction monarchs would "J" and pupate (in its pre-pupa stage, a monarch is said to be "J"ing due to the fact that they hang with their heads curled upward, forming a tight "J").

Before performing this experiment, I was of the opinion that a monarch's "J" would be greatly influenced by magnetism. Also, my science teacher, Mrs. Cansler, had informed me that there were small bits of metal in a monarch that were highly magnetized, which seemed to support my theory.


The observations are as follows:

  • In the two boxes containing north facing magnets, I had one larva "J" southeast, three "J" west, and two "J" north.
  • In the two boxes containing south facing magnets, I had one larva "J" east, one larva "J" northeast, two larvae "J" west, and one larva "J" southeast.
  • In the two boxes containing no magnets, I had two larvae "J" east, one larva "J" north, two larvae "J" south, two larvae "J" southwest, and one larva "J" northeast.
(Photo: Chris Ramage)
(Photo: Chris Ramage)
(Photo: Chris Ramage)


After trying twice to raise a clutch of monarchs from eggs, both times with limited success, I got ten monarch larvae from Mrs. Cansler, giving me a total of 21. I placed them in 6 separate shoe boxes, 2-4 larvae in each box. I oriented the boxes with a compass so that one end pointed to magnetic north. Then I taped a strong magnet to the north sides of two of the boxes and to the south sides of two of the boxes, leaving two boxes without magnets to serve as controls. The boxes were spread out around the house, so that the magnets would not interfere with each other. I observed the larvae daily until they "J"ed and then recorded the direction of the "J"ing. The total number of larvae observed "J"ing was only 19; one larva escaped (we found him pupated in our fireplace, but I didn't know which way he had "J"ed) and the other was eaten by a spider.


From this information, I can only conclude that magnetism has no effect whatsoever on the "J"ing of monarch butterflies. The relatively small sample size may have been at fault, but this is still highly unlikely. Mrs. Cansler, my teacher, attempted a similar experiment. She placed a strong magnet on the top and bottom of her containers. This created a strong electromagnetic field around the container. Though slightly different, her experiment had similar results; the monarchs "J"ed in all directions.

At the same time, my science class was conducting an experiment to see if monarchs would "J" towards light. They set up several boxes so that light would come in through only one end. The results: all the monarchs "J"ed in the same direction. This makes me think that the "J"ing of the monarchs is completely governed by the direction from which the light is coming.

Follow-Up Experiments

  • Do the same project, using a larger sample size.
  • See if exposure to magnetism will affect the butterflies' adult life.
  • See if magnets will affect the gender of the butterflies.
  • See if magnets will affect the butterflies' ability to migrate.
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