Answers From the Monarch Butterfly Expert
Spring 2011
(Back to Monarch Butterfly FAQ)

Special thanks to Dr. Karen Oberhauser for sharing her time and expertise again this year to answer readers' questions.

Have you ever wondered:

  • What is the longest a monarch could live?
  • Why does it look like monarchs have only 4 legs?
  • Do they have unique wing patterns, like fingerprints?
  • How can I help the monarch through its migration?
  • How has global warming affected monarchs?
Teaching Suggestions
Teachers: You can use today's Answers from the Expert in the activities suggested in "Learning from Experts."


Dr. Karen Oberhauser

Dr. Karen Oberhauser
Professor at the University of Minnesota. Director of the Monarch Larva Monitoring Project and Monarch Lab.

From Maryland:

Q: What is the longest time a Monarch could live?

A: Monarchs that migrate south in the fall, and north in the spring, live longest. The longest that these butterflies live as adults is probably about eight months.

Q: Which nectar plant is the most popular food for the Monarch butterfly?

A: Monarchs nectar from many flower species, and their favorite species vary a great deal because different nectar flowers are available at different times of the year and in different locations. They generally like yellow and purple flowers, but also use red and white flowers.

Q: What type of caterpillar turns into a Monarch? Is it a Monarch Caterpillar?

A: Yes!

From New York:

Q: I know Monarchs are an insect, but when it lands on your finger there are only 4 legs holding on to you. Where are the other 2, and are they ever used, or are just tucked in someplace.

A: All butterflies in the family Nymphalidae (like monarchs) look like they only have 4 legs. The front pair of legs is tucked up under the head and thorax.

From South Carolina:

Q: Do butterflies have unique wing patterns, the way people have unique fingerprints?

A: Great question. There definitely are differences, but I'm not sure if they really are unique to each individual.

From North Carolina:

Q: My second graders would like to know if you hold the butterfly wings too long will they die?

A: As long as you hold them carefully, without rubbing the wings and thus causing the scales to fall off, holding them won't kill monarchs.

Q: Will some butterflies die because their wings are too torn to fly?

A: If their wings were too torn to fly, they would die.

Q: Is there a way you can help a butterflies wings be repaired?

A: I have never done this, but I've heard of people repairing the wings with small pieces of paper and glue.

From New York:

Q: What is difference physiologically about the 4th generation of Monarchs that makes them fly further, live longer and behave differently from the first 3 generations? What causes the differences?

A: The migratory generation of monarchs is in a physiological state called "diapause". These individuals are reproductively immature (the females do not produce eggs and the males have undeveloped reproductive organs). This is caused by lower levels of a hormone called juvenile hormone, and allows them to live longer. Recent work by a group at the University of Massachusetts has shown that diapause and migration are controlled separately.

From Wisconsin

Q: Do you think it is possible to greatly increase the number of eggs/caterpillars that survive to maturity (butterfly stage) by trying to control predators? If so, is there a good resource that identifies the most common dangers to the developing monarch stages and how they might best be dealt with?

A: There is little you can do to control predators that won't also harm monarchs. The most important thing you can do to support monarch development is to create and preserve habitat, and avoid the use of pesticides that can harm them.

From Ontario:

Q: How can I help the Monarch through its migration? What can one individual do to help?

A: You can make sure that any land over which you have control contains appropriate monarch habitat (milkweed, nectar sources, and no insecticides). You can also encourage your friends, neighbors and family to do the same; write letters to encourage habitat preservation and restoration in public land; and try to slow down development that removes habitat. You can also support organizations working to preserve monarch and other pollinator habitat.

Q: How has global warming affected the butterflies?

A: At the University of Minnesota, we're working to develop predictions of how climate change may affect monarchs. Because they face many other environmental challenges, it is difficult to assign current changes in numbers or migration patterns to a single cause, like climate change. However, our models predict that monarch overwintering sites will become much wetter than they are now, possibly resulting in more frequent storms that cause mortality of large numbers. It is also likely that much of their current summer habitat will become too hot, so they may need to move farther north for breeding.

Q: Does urban sprawl and over development change the path of the Monarch migration, or will they continue to try and work their way around the infrastructure? I live in Ontario, Canada, and I have been following the butterflies through this site for many years. Since urban sprawl has surrounded our area, I have noticed a decline in sightings of the beautiful Monarch.

A: It's hard to determine just how the infrastructure of human habitation affects monarchs as they breed and migrate. We do know that we often see them in densely-populated areas, so they can definitely use these areas. However, the lower density of appropriate habitat will decrease the number of monarchs that you see.

From New York

Q: I am visiting in Fort Myers, Florida and noticed (and photographed) Monarchs at Lakes Park the other day. Are these Monarchs year-round residents or will they migrate too? Q: If they are year round, do they have continuous broods? Q: If they will migrate, will they follow the same three generations to get "home" as those coming from Mexico?

A: Great questions. In most years, monarchs do breed continuously in much of southern Florida. However, in some years this breeding population suffers freezing conditions that cause high levels of mortality. We know that there is some migratory movement between this population and the rest of the eastern migratory population, but the degree to which monarchs in Florida fly north in the spring is unknown.


From California:

Q: What is the minimum survival temperature for all stages of Monarch development? So far, I have seen caterpillars survive 28 deg temps here in Southern California.

A: There haven't been a lot of experiments done on egg, larval, or pupal survival. I'd be really interested in your reports on their survival of freezing temperatures, as we're beginning to study that at the University of MN.

Q: Have you ever super-glued a broken primary wing successfully? I did and watched it fly (powerfully) away, after spending three cold night in the garage entirely dormant with only an occasional twitch of antennae to indicate life.

A: No, I haven't done this.

Q: It appears our Monarchs don't leave the area (Moreno Valley, CA) but overwinter. Of course, I can't swear to it, as I don't tag, but individuals with damaged wings are hard not to I.D. Is this the new possible as the planet heats up? .

A: This is definitely possible. Monarchs appear to overwinter in many areas in the southern US, sometimes breeding and sometimes not.

From New York:

Q: I would like to know if anyone has plans for an outdoor hatchery to use in a homeowner's conservation efforts. I plan to attempt to build one this spring. Any help I could get would be great, so I don't have to bring the cats inside again!

A: In my opinion, the most important thing that we can do for monarchs is to preserve their habitat, rather than focus on rearing individuals. But, you can definitely learn a lot about monarchs by rearing them, so I don't want to discourage this as long as you're careful to prevent diseases when you rear them in crowded conditions.

From New Jersey:

Q: How did people discover what monarch butterflies ate?

A: They observed them outside eating milkweed and nectaring from many flower species.

Q: How were monarch butterflies discovered? How did people find out where monarch butterflies lived?

A: People have always been interested in the plants and animals that they observed, and this is how they learned about monarchs and where they live.

From Kansas:

Q: Last year my husband and I raised close to 37 monarchs from eggs (off our dill plants) to caterpillars to beautiful monarch butterflies. The first 2 batches were great but then we ran into a problem with the crystillas turning black and not developing. We cleaned the large fishtank we were using but still had very little success. We had also put Fritillary caterpillars in the same tank. We are wanting to do this again this year as our grandchildren really loved watching the process. Any idea's?

A: First, if you got the caterpillars from dill plants, you were rearing black swallowtails and not monarchs. It is possible that the ones at the end of the summer were overwintering in the pupa (chrysalis) stage, and were not really dead. Swallowtails do not migrate, but spend the winter as pupa. The best way to rear caterpillars of any kind is to prevent overcrowding, keep the containers clean, and keep their food fresh.

From Pennsylvania:

Q: Do you feel that the monarch sanctuaries are safe with respect to the violence that has been going on in Mexico? I am hoping to make the trip next February and I realize that the situation can change but for now, what is your take on the situation?

A: Shile the violence in Mexico is frightening, I do not know of anyone who visited the colonies this year and had any problems.

From Wisconsin:

Q: What is being done about the Oe parasite that is affecting the Monarch population? Many of the butterflies I tested last summer had it.

A: If you were collecting wild butterflies, there really isn't anything that can be done about Oe. However, if you were rearing the larvae, it is possible that you were collecting milkweed that had been contaminated by infected females. I try to avoid collecting plants that have eggs or chew marks from larvae. The folks at Project MonarchHealth are observing increasing infection rates from Oe in the eastern migratory population, and aren't really sure what is causing this.

From Indiana:

Q: I know that the monarch drinks flower nectar while in Indiana in the summer, but what do the over-wintering monarchs eat while in Mexico? Are there lots of flowers for them to nectar on during the winter in Mexico? Or do they not eat much during the winter?

A: Most of the monarchs in Mexico survive using the fat stores that they built up as larvae or as they migrated south in the fall. There are some flowers in the wintering sites, but not enough for all of the butterflies that are there.

From Texas:

Q: If caterpillars eat a plant bare, will they move to another or starve?

A: This really depends on how close another plant is and how old the larvae are. They definitely do move between plants, but the earlier instars are less likely to do this, and they are less likely to successfully move very long distances.

Q: Will adults die if they drink nectar from a plant treated with systemic pesticide? How long does the chemical stay in the plant/ should it be quarantined before planting?

A: Yes, systemic pesticides can kill butterflies that consume nectar from treated plants. I recommend avoiding any pesticide use on plants that provide nectar. I'm not sure how long these pesticides last.

Q: I have butterflies and caterpillars in my yard until December (Houston). What can I offer as nectar for the late hatch? Hummingbird mix? Gatorade?

A: I recommend flowers!

From Vermont:

Q: What is your opinion about an organization, such as a Hospice, releasing live Monarchs during an event to honor those people who have passed in the last year? I have been contacted by them as a contact person to answer their questions about Monarchs. The organization wants to buy live Monarchs from Swallowtail Farms and have the insects shipped to them. I don't know how I feel about this or even if it is the right thing to do. Is Swallowtail Farms a good place to order from? Is there anyone else that you can recommend? Any guidance you can give me is very much appreciated.

A: This is a complicated and controversial issue, with many people having strong opinions. Personally, I don't think that living organisms should be released in ceremonies such as this, unless there is a strong education or conservation component to the release. However, many intelligent and conservation-minded people disagree with me. I think it's a decision everyone has to make for themselves. There are risks to these releases – the butterflies could be released at times or locations that are inappropriate, there is a chance that diseases may be spread, and these releases may affect our ability to understand natural patterns of monarchs. However, in some cases, educational value might outweigh these risks.


From Minnesota:

Q: Do the Monarchs in South America and the Southern Caribbean overwinter in Mexico also? I've followed the Monarch migration from North America to Mexico for several years. In February we were in Bonaire N.A. and saw many monarchs.

A: Little is known about the details of migratory and overwintering behavior for monarchs in South America and the Caribbean. It is likely that many of them breed continuously.

From Pennsylvania:

Q: I live in the Philadelphia area and have a butterfly bush in my back yard. Are monarchs known to visit this part of the country?

A: Yes! You should plant some milkweed for them, and you would be very likely to get some eggs and caterpillars in your yard.

From Pennsylvania:

Q: I have a small butterfly garden near our house. The Monarch caterpillars have climbed over the brick to form their chrysalis on the eave of the garage. I have wondered if the caterpillar could damage its skin in the process. The success in butterflies emerging has been poor but I have not kept data.

A: I would be surprised if the monarchs were damaged by crawling over the brick. I wonder if it too hot for them on the eaves of your garage. It would be interesting to actually keep the data and see what the survival rates are.

From Texas:

Q: Do you lead groups to Mexico to experience the Monarch sanctuaries so that more can be learned about this incredible butterfly? If so, are they open to the public? What a dream experience that would be!

A: Sorry, I don't lead group tours to Mexico. There are several good tours available – I'd recommend asking people on the dplex listserv for their recommendations.

From Texas:

Q: As the monarchs pass through San Antonio, what will they be eating/surviving on? In the fall, I make sure they have the right flowers, but what for now?

A: They definitely need nectar sources in the spring, so you should plant what's appropriate for your area at that time of year. I'm not as familiar with spring flowers in Texas, but up here (in MN) monarchs use dandelions, lilacs, flowering shrubs (like Viburnums), and many other spring flowers.

From Indiana:

Q: I am presently on the island of La Gomera in the Canary Islands Spain. They claim to have Monarch butterflies (I have not seen them) here and I have seen them in New Zealand. How many different populations exist and are they the same.

A: Monarchs are frequently seen in the Canary Islands (how lucky for you to be there!), where there is an established population. The same is true in New Zealand. It is likely that these populations have been established fairly recently (within the last 100-150 years), from the North American population. They are the same species.

From Missouri:

Q: Do Monarchs tend to roost in the same spot year to year, during migration, and do they usually roost around sundown? Do they normally leave their roost at sunup?

A: Sometimes monarchs use the same roosting spots year after year, and sometimes they appear to use spots that have never been used before. Data contributed by Journey North observers are really helping to understand the details of fall roosting. (See maps of fall roosts during migration.) They do not fly at night, so the roosts generally form as it gets dark (or cold), and break up when it is sunny and warm the next day.

From California:

Q: I would like to know what the monarchs that live in California do, since they don't go to Mexico. They seem to be in Southern California from August until March. I have had several hatching even recently.

A: Some monarchs in the western US appear to breed all year, and some go to roosting sites along the coast of California.

Q: So, how did they loose the migration instinct? Are they becoming a separate species? Perhaps this group will be all that is left in the future if Mexico destroys the overwintering grounds. Not much time is spent on the website looking at this population and I wonder why.

A: Most of them still do migrate. In both the eastern and the western population, some monarchs continue to breed in the fall and winter, perhaps in response to the availability of their milkweed host plants. Regarding your point about Mexico destroying the overwintering grounds… We really need to consider the importance of preserving habitat in the US as well as Mexico – while the overwintering grounds are very important, so are the breeding grounds and migratory pathways in the US and Canada.

From Louisiana:

Q: I have had monarchs in my yard in late October and November laying eggs and caterpillars hatching out. I thought that this 4th generation of monarchs migrates to Mexico and does not mate/lay eggs until Spring of the next year.

A: Some monarchs do breed in the fall. It would be interesting to know what species of milkweed you have in your yard. If it is the non-native tropical milkweed, its presence may actually be causing the monarchs to stop in LA to breed instead of continuing to the Mexican overwintering sites.

Q: Do monarchs overwinter in a chrysalis or as a butterfly in the lower south of USA?

A: As a butterfly, although in areas where there is continuous breeding, all stages are present.

Q: Do you know the ~ projected date that the monarchs are going to leave Mexico this year?

A: I'm writing this on March 19, and they are leaving! There have been a few sightings in the southern US.

From Florida:

Q: Misting, some say to mist the cats, plants and chrysalis every day. Some say Just the plants. With a indoor enclosure, how often and what should be misted?

A: I don't mist monarch caterpillars when I'm rearing them, but make sure that the milkweed I give them is fresh and moist. I also don't mist the pupae.

From Virginia:

Q: I gather monarch eggs off the milkweed that I plant, bring them in, and transfer the small caterpillars into a 1 gallon aquar. I keep them there until they are large enough to see, then transfer to a 20 gallon aquarium. I have pretty good luck with this . but occasionally I lose some as caterpillers, and others when they can not seem to break out of the crysalis? Can you give me any helpful hints of what I need to do to help and not lose any. I gather them as eggs to avoid the tachinid flies. Thank you so much...

A: You'll always have some mortality. We have the highest success when we rear monarchs separately, so that if some do have a disease, it is less likely to be transmitted to others. For the detailed rearing instructions that we use, see

Q: I have ordered tags to tag some of my monarchs this year. Can you tell me how this works?

A: There are great instructions about tagging monarchs on the Monarch Watch website.

Q: I am really interested in going to Mexico to see the Monarchs during Migration.. When is the best time to do so, Fall or Spring? and approx timing. Also do you know of tours that do this? Or do you do one? A: Sorry, I don't lead group tours to Mexico. There are several good tours available – I'd recommend asking people on the dplex listserv for their recommendations.

From Texas:

Q: Do you know how big the winter population of the over-wintering monarch colonies in Mexico this winter was as compared to previous winters?

A: This year there were about 4 hectares of forest occupied by monarchs. This is about twice as many as last year, but because last year was the lowest on record, it was still lower than the average over the last 18 years of just over 7 hectares. (See graph.)

From Louisiana:

Q: I visited El Rosario Reserve in 2000. There was much concern about the logging practices in the area and how it would affect the Oyamel Fir forests and the dwindling habitats for the Monarchs. Has there been any action to stop the logging practices and how much of the reserves are left?

A: There is a lot of work being done to stop logging in Mexico. For a background on some of this work, see the Monarch Butterfly Fund website ( - this work involves education, reforestation, and research to understand the best ways to preserve the forests that remain. The MBF website includes maps on the amount of land in the Reserves.

Q: Do you see a permanent decline in the Monarch population?

A: Monarch numbers fluctuate a great deal from year to year, so it is impossible to tell if the declines we've seen are permanent or just what is causing these declines. The area occupied by monarchs in the overwintering sites has been below average for the past several years. There is an excellent graph showing this trend on the Journey North website:

From Pennsylvania:

Q: Last year, for the first time, I had a few caterpillars stop eating before they were full grown. The chrysalises of these smaller caterpillars were obviously smaller also. The emerging butterfly was also smaller. Why did they do this and is the smaller butterfly less likely to survive? This did happen in the fall but I had them indoors so the caterpillars wouldn't have been aware of the outside conditions and temperatures.

A: There is a great deal of variation in monarch size. If they were being reared late in the season, there may be some selective pressure to develop quickly to increase their chances of getting their migration underway before freezing temperatures made this impossible. Even though these monarchs were inside, they were probably exposed to outside daylengths, and thus "knew" how late in the fall it was.

From Washington:

Q: We happen to be traveling near the North side of the monarch winter grounds and would like to know the best way to visit the monarchs.

A: It's a little late for this answer (at the time I'm writing), but you can easily hook up with rides into the sanctuaries in any of the nearby towns.