Answers From the Monarch Butterfly Expert
Spring 2004
Courtesy of Dr. Karen Oberhauser

(Back to Monarch Butterfly FAQ)

Special thanks to Dr. Karen Oberhauser, University of Minnesota Department of Ecology, Evolution and Behavior for providing her time and expertise in responding to your questions below.

Thanks for all of your great questions! If you'd like to learn more about monarchs, you might want to check out our two websites for basic information on monarchs:

Monarchs in the Classroom, and for information on the Monarch Larva Monitoring Project and our findings.

From: C.J. Davenport School
Egg Harbor Township, New Jersey

Q: Why do the female Monarchs have more poison in their bodies than the males?

A: This is a consistent pattern, but I don’t think anyone knows why females sequester more toxins than males. It’s also possible that they sequester the same amount but that the toxins break down more rapidly in the males.

Q: How do the Monarch predators survive after the Monarchs leave in March?

A: There are two important bird predators, the black-headed grosbeak and black-headed oriole. The grosbeak is migratory, and spends summers in the western US and southwestern Canada. The oriole stays in Mexico, but probably eats other insects during the summer when monarchs are gone.

Q: Is it better for the Monarchs to live in a sanctuary with a thick canopy or a thin? We thought thick for protection but one of my students realized there would be very little sunlight if the canopy was thick.

A: Even though there is more sunlight in the thinner canopy, the monarchs receive important protection from the thick canopy. The canopy modulates climatic effects, keeping warm air in at night-time after the sun sets. It also helps to protect the butterflies from rain and snow. Although the effects of very warm weather have not been well-studied, it is also likely that conditions that are too warm speed up the butterflies' metabolism, thus increasing the rate at which they burn up their energy reserves. Open areas warm up more during the heat of the day.

From: Hollingworth Center
New York, New York

Q: We learned that a monarch butterfly takes between 10 and 14 days to emerge from its chrysalis. But we had a lively male monarch that emerged after 40 days! It was a bit of a shock. On September 20th, the chrysalis was formed. (We had found the caterpillar on a milkweed plant we had purchased a week or so earlier.) On October 29th the monarch butterfly came out of its chrysalis. We had kept the tank with the chrysalis in our sun room in Connecticut. The temperature in the room was about the same as the temperature outside. We released the butterfly after it had dried out. If flew away. Why do you think this monarch butterfly came out so late from its chrysalis?

A: I'd really need to know what the temperature was in your sun room. We’ve had monarchs take this long to emerge from the pupa stage when they were kept in very cool conditions, but not at room temperature. If it really was the same temperature in your sun room as it was outdoors, I guess the 40 days doesn’t surprise me. You should look up the term degree-days on the web. Insects, being cold-blooded, develop at different rates in different temperatures. Degree-days take into account both time and temperature, and are used to measure development time in insects.

From: Sixth Grade Academic Center
Jonesboro, Arizona

Q: We are curious about the activity of various insects and their dependence on our milkweed plants. How can we learn more about them? Is there a guide that could help us identify the invertebrates other than the monarchs that are eating our milkweed plants?

A: There is a new field guide just about insects that live on milkweed. It’s called Milkweed, Monarchs and More: A Field Guide to the Invertebrate Community in the Milkweed Patch, and was written by Ba Rea, Mike Quinn and myself (Karen Oberhauser). You can get one from Monarchs in the Classroom for $9

Q: How many animals' life cycles are dependent on milkweed?

A: Dependent on is kind of a complicated term. Many insects live on and near milkweed; they use it as a source of nectar or larval food, or they eat insects that are on the milkweed. Some just use it as a place to rest. The field guide described above describes hundreds of kinds of insects, and all of the insects on milkweed aren't even included!

From: Rolling Meadows High School
Rolling Meadows, Illinois

Q: During the winter when the butterflies are on their way to Mexico, what is their main cause of death?

A: I don't think anyone knows this for certain. Some are eaten by birds, some are hit by vehicles, and some are blown off course. Others probably run out of energy reserves or can't find enough water. The most important sources of mortality are probably very dependent on the weather – in very hot conditions, I would guess that fewer survive.

Q: During the winter when the butterflies are on their way to Mexico, what do the butterflies do if they are blown off their path? How do they find their way again?

A: The question of how monarchs find their way during migration is complicated, interesting and wonderful! There is a chapter in a new book coming out about monarchs (The book is The Monarch Butterfly: Biology and Conservation, edited by Karen Oberhauser and Michelle Solensky and published by Cornell University Press, and the chapter is by Sandra Perez and Chip Taylor) about this question. Perez and Taylor took monarchs from the central US to the east, and vice versa, and found that the butterflies shifted their flight direction depending on where they were. This suggests that they can somehow sense where they are after being blown off course, and adjust their flight path accordingly.

From: Garfield Elementary
Brainerd, Minnesota

Q: Can two monarch caterpillars hatch from the same egg or in other words are there ever twins?

A: Interesting question!! I've never seen or heard of this, and couldn't find anything about insect twins in any books. If anyone knows the answer to this one, please let me know! (Karen Oberhauser).

From: Woodruff, Wisconsin

Q: I live in Wisconsin and have a very special interest in the Monarch Butterfly. I am aware of schools in our State that participate in observing the life cycle of the Monarch by obtaining rearing kits that contain a milkweed plant, monarch larva and a cylinder in mid-April to mid-May. My question is this. What happens to the Monarch Butterflies that are released in an area before milkweed is available to them due to a later growing season?

A: If the milkweed doesn't come up during their lives, they die without reproducing. However, there should be milkweed available in Wisconsin by mid-May, so even the monarchs that are obtained in April should have milkweed available when they are released as adults.

Q: What happens to the Monarch Butterflies that students release in the Spring in an area that frequently has freezing temperatures until June 1st?

A: Monarchs can withstand short periods of freezing temperatures, as long as the temperatures are not too much below freezing. Anderson and Brower found that they could withstand temperatures as low as -8 degrees C, as long as they were dry.

Q: What happens to the Monarch Butterflies that students release in the Spring in an area where nectar plants are not yet readily available?

A: If nectar is not available soon after the monarchs are released, they will starve to death.

From: Powell County Schools
Slade, Kentucky

Q: Hello, We could only find limited general information about what happens inside the chrysalis. We would like to know more specific details about what happens inside as the larva changes into a butterfly. We read some information that said the larva liquifies - does it melt? This doesn't make sense to us. We are confused, usually things become liquids when you heat them up. If it does turn into a liquid, how does it become a solid butterfly?

A: While the process of complete metamorphosis looks like four very distinct stages, continuous changes actually occur within the larva. The wings and other adult organs develop from tiny clusters of cells already present in the larva, and by the time the larva pupates, the major changes to the adult form have already begun. During the pupal stage this transformation is completed; in many ways it’s similar to the process of development that occurs in a human embryo – organs form and grow from specialized cells. Despite what some books say, the monarch does NOT turn into liquid during the pupa stage. I’m not sure where this mistruth started – maybe someone dissected a dead one and it had liquefied. You can read a lot more detail about the process of metamorphosis in a good insect encyclopedia or on the web.

From: R.L. Norton elementary
Snellville, Georgia

Q: Dear Dr. Oberhauser, I just returned last week from the Monarchs Across Georgia trip to Mexico. We were able to see El Rosario, Herrada and Chinqua sanctuaries with Dr. Calvert. It was a wonderful trip and now I am hooked on Monarchs even more! My students and I have been observing the migration map, and notice the overwintering grounds in Florida and the Gulf Coast. What trees do the butterflies roost in in the U.S.?

A: I'm glad that you got to go to Mexico with Bill Calvert! In California, monarchs roost, for the most part, in Eucalyptus trees and Monterey pines. These are the trees that grow in the sites where conditions are best for overwintering. They don’t have large congregations in Florida and the Gulf Coast like they do in Mexico and California, and in many cases, butterflies overwintering in these areas are still reproductive (as long as there’s milkweed available). Thus, you wouldn’t see roosting trees in these areas.

Q: I will be leaving Georgia this fall to live in South Carolina. Does the Monarch migration travel through the western side of South Carolina? I want to continue my studies with Journey North, and Monarch Watch with students there.

A: Yes! Good luck with your move!

Q: We have planted the milkweed known as Asclepias curravasica in our Outdoor Habitat. The past three years it has done very well. We collect seeds and then replant first in grow labs in the spring. Are we wasting time and is it actually a perennial? Thank you for answering our questions! Mrs. Glawe's Third Grade, Norton Elementary, Snellville, GA

A: It is a perennial in areas where it doesn’t freeze. I think it’s safest to collect the seeds and grow the plants as you do, since there is a chance that you’ll get a freeze in the winter. Plus, your students get the great experience of actually growing the plants for the monarchs.

From: Notre Dame Elementary School
Burlington, Iowa

Q: Do monarchs return to same roosting spots each year during the fall migration as they come through North America? We had a roost in our back yard in Burlington, Iowa this past fall, and I was wondering whether monarchs would roost there again this year on their way to Mexico?

A: Sometimes yes and sometimes no. There are sites that are used year after year, but there are also sites that are only used once. This is an incredibly interesting phenomenon, and one that deserves a lot more study.

From: First Baptist Christian
Weymouth, Massachusetts

Q: A question I get every year when we study the metamorphosis of the monarch is: What are the gold spots on the chrysalis and how did they get there? Why and for what purpose are they there? I have asked many people who have some knowledge of the monarch and have never gotten a clear answer. Thank You

Fred Urquhart first studied the gold spots on monarchs in the 1970’s. He felt that the spots were involved in the distribution or formation wing scale coloration. However, the experiments that he did involved cauterizing 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 used for:

a) Camouflage – they could reflect colors of the surroundings and break up the shape of the pupa; they might also look like dew droplets.

b) Warning coloration

c) Filtering particular wavelengths of light which might be harmful to the monarchs

d) They might not have any function, but just be the result of something else in the cuticle of the insect.

From: Sappington School, LEAP program
St. Louis, Missouri

Q: We are reading about the monarch butterfly and reproduction. We know the female lays eggs. We know she needs a mate. But, how does the monarch butterfly mate?

A: Monarch courtship is unusual among the Lepidoptera in that males sometimes force females to copulate and appear not to use chemical courtship like most other butterflies and moths do. Males initiate mating attempts by pursuing females in the air, often forcing them to the ground and engaging in a long ground struggle. The male probes the female with the tip of his abdomen while the female appears to resist. About 30% of these mating attempts end in copulation; when it does, the male successfully attaches the end of his abdomen to the slit that you can see in the bottom of the female’s abdomen. Both females and males often mate several times during their lifetimes.

From: McKinley Elem.
Billings, Montana

Q: How long would it take for a monarch to fly from Mexico to Montana?

A: This would depend on temperature and wind conditions. On average, it probably takes about two months, total. However, this would also depend on where in Montana the monarch starts.

Q: Who first discovered the Monarch butterfly?

A: I’m not sure what this question means. Humans don’t really discover other species. We notice them in our environment and give them names, but many groups of humans in many areas probably noticed monarchs at different times. Monarchs were given the scientific name Danaus plexippus by Carolus Linneaus, who established the modern binomial system of nomenclature (genus name plus species name) for plants and animals.

Q: How many Monarchs are there estimated to be in the world?

A: I don’t think anyone has ever calculated this. There are monarchs in North and South America, many islands in the Pacific Ocean (including Australia and New Zealand), and other places (see Monarch Lab ). The number would depend on the time of year and would vary between years; if I had to give a number it would be in the 100’s of millions.

From: Upland Hills School
Upland Hills, Michigan

Q: Would the monarchs migrate somewhere else if the oyamel forest was wiped out? Would they know to go somewhere else?

Unfortunately, we don’t know the answer to this question. The oyamel forests provide specific climatic conditions needed by the monarchs, and areas that have these conditions are rare.

Q: Do monarchs sleep?

We don’t know if they actually sleep, but they do not fly or move very much when it’s dark.

Q: Have you ever kept a monarch through the winter in the laboratory? If so, how long did it live?

Yes, we keep monarchs through the winter every year. We keep them in a 10 degree C incubator, and feed them every 10-12 days. They last all winter. We're actually just pulling some out in the next few weeks to start our 2004 lab population.

Q: How come some of the butterflies we raised fell off the chrysalis when their wings were still hardening?

It could be that they were bumped, or that they were too weak to hold on to the chrysalis for some reason. In some cases this happens when the butterflies are infected with the protozoan parasite Ophryocystis elektroschirra; you might want to read about that on the Monarch Lab or Monarch Watch websites.

Dr. Karen Oberhauser
University of Minnesota

St. Paul MN 55108