Answers From the Monarch Butterfly Expert
Spring 2000

Courtesy of Dr. Karen Oberhauser
(Back to Monarch Butterfly FAQ)

Special thanks to Dr. Karen Oberhauser for providing her time and expertise in responding to your questions.

  • Visit Karen's "Monarchs in the Classroom" education program Website called "MonarchLab"

R.L. Norton elementary

Q. Dear Monarch Expert, My class has been very interested in Monarchs. While we were watching for them in our butterfly garden last fall we notice a few monarch wings underneath the butterfly bush. We kept finding more and more wings underneath the bush. I have been keeping them for the students. We want to display them. First question: What caused all of the wings to be there? We saw no bodies.

A. Great question! It sounds like a bird was eating your monarchs. You probably know that there have been several studies of bird predation in the Mexican overwintering colonies. There are also many reports of birds eating monarchs in the overwintering sites in California, and at other places in the US. However, there haven't been as many detailed studies of bird predation outside of Mexico. We know that the cardiac glycosides that monarchs eat as larvae give them some degree of protection from birds, but this protection isn't perfect!

Q. What would be a good way to display our wings?

A. Get some tape that is used to bind books or put over mailing labels. It should be 3-4 inches wide. Carefully place the wings on a piece of this tape, and put an index card or a piece of an overhead transparency over the wings. If you use the overhead, you'll be able to see both sides of the wings. If you use an index card, you'll need to make separate cards to see the top and bottom of the wings. Label the cards with the species name, gender, where and the specimen was found, and any other information you'd like to include.

Q.How should we handle the wings? Thank you very much! Anne Marie

A. Monarch wings are pretty sturdy, so as long as you aren't too rough with them, they should be fine. Even if they aren't in perfect condition, the nicks, tears, scratches and worn spots will be interesting to observe.


Q. Since Monarchs follow a pattern going either to Mexico (from the east coast, Canada, and the midwest) or California from the west coast, what happens when Monarch suppliers send larvae or pupa Monarchs through the mail to places other than where those Monarchs would normally live?

A. I don't know of any monarch suppliers who send monarchs from the east to the west, or vice versa. This would be very irresponsible, and illegal without a permit.

Q. Why are they allowed to do this?

A. Great question! Anyone who ships monarchs to sell across state lines needs a permit from the USDA. Permits wouldn't be granted to sell monarchs from the west coast to states east of the Rockies, or from east of the Rockies to the west coast. Another issue is whether people should be allowed to send monarchs from, say, Minnesota to New York. Even though monarchs in these two states are both from the eastern population, we don't know for sure that they aren't somewhat genetically different.

Permits only regulate states to which monarchs can be shipped. If I had a permit to ship monarchs from here in MN to you in NY, it would be up to the two of us to make sure that the monarchs were released in places that they could find food for themselves and their offspring. People don't always do this, and this is clearly not very good for the monarchs. It could also confuse scientists interested in studying the actual range of monarchs; if we find a monarch in a place with no milkweed around, we can never be sure if it is there naturally or if someone released it. This is a problem.

Q. Are there any oyamel trees anywhere in the US?

A. Not that I know of, but there might be relict populations somewhere.

Q. What tree are they most similar to that can be compared to an oyamel tree in the US?

A. Oyamel firs are closely related to firs that do grow in the US, and look just about the same to me as the firs we have here.

Q. What kind of trees do they overwinter in, when they are in California?

A. If you've ever been to the coast of California, you'll have noticed that most of the trees there are eucalyptus trees, and this is the main tree that the monarchs use. They also use pine trees where these are growing near the coast, and just about any other kind of tree that is growing in the right locations.

Q. What steps is the Mexican government taking to stop the destruction of oyamel trees in Mexico?

A. The government is reviewing the decree that originally protected the overwintering sanctuaries in 1986, and getting input from many people with scientific knowledge of the locations of monarch overwintering sites and needs of the monarchs. They are also consulting with people who understand the needs of the people living in the area, and supporting programs that will provide alternative sources of income for the landowners.

Joyce Middle School

Q. We know that no one seems to know the function of the gold dots on the monarch chryslais. We have developed several theories of our own, such as, a warning signal that monarchs taste bad, or as camoflage because the dots look like dew. We were wondering, have any experiments or specific observations ever been done to determine the purpose of the dots? Ms. Cerullo's 7th grade science classes, Woburn, MA

A. Yes. Fred Urquhart did work in on this in 1970's. He felt that the spots were involved in the distribution or formation wing scale coloration. However, he did experiments on this in which he cauterized the gold spots on the pupa, and it is possible that this process may have damaged the underlying tissue and affected the color patterns. Interestingly, all danaine butterflies (monarchs and their relatives) have metallic spots on them. A group of researchers in Germany did a careful study of the properties of these spots. I'm not going to summarize all of their work because it goes into a lot of detail about the structural and optical properties of the spots. However, they hypothesized that the spots might be useful for:
  1. camouflage (as you suggest) - they could reflect colors of the surroundings and break up the shape of the pupa; they might also look like dew droplets.
  2. Warning coloration (as you also suggest)
  3. Filtering particular wavelengths of light which might be harmful to the monarchs
  4. They might not have any function, but just be the result of something else in the cuticle of the insect.

Q. When the newly emerged adult monarch pumps fluid from the abdomen into the wings, does the fluid remain a liquid in the veins or do the veins of the wings become solid after awhile? Ms. Cerullo's 7th grade science classes, Woburn, MA

A. Blood flows through the wings even after the wings have hardened. Blood flows from the thorax into the wings, and then back into the thorax.

Dr. Karen Oberhauser
University of Minnesota
Department of Ecology
1987 Upper Buford Circle
St. Paul MN 55108
612 624-8706 fax: 612 624-6777