Monarch Biology

What is the function of the gold dots on a monarch chrysalis?

Fred Urquhart first studied the gold spots on monarchs in the 1970s. 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. They are not metallic (so they aren't really gold), but the cells reflect light like metals do, giving them the appearance of being metallic. Other danaids have silver, copper, or gold spots.

Here are some hypotheses for the reasons that these butterflies have metallic-looking spots on their pupae:

1. Camouflage -- 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
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.
5. Oxygen exchange

Do monarchs live in other parts of the world besides North America?

Yes, monarchs are found in many places throughout the world, but they probably originated in the Americas, and were spread either with the help of humans or on their own to other places. They are found in Australia and New Zealand, and many islands east of these countries (most islands between Australia and Tahiti have monarchs). They are also found in Hawaii, most islands in the Caribbean, and even sometimes in western Europe.

How many miles can a monarch fly in one day?

In general, about 25-30 miles. When weather conditions are favorable, they may be able to go further, but poor weather conditions may also prevent them from traveling at all! Many factors influence how far monarchs can travel in one day, so it is quite variable.

How are monarchs toxic to predators?

Monarchs become toxic to predators by sequestering or storing toxins from the milkweed plants that they eat. Milkweed contains toxins called cardenolides, or cardiac glycosides, which are toxic to predators. This makes monarchs very distasteful or unpleasant to predators. Some predators have evolved ways to avoid or tolerate these toxins, such as the bird predators found in the Mexican overwintering colonies.

How do monarchs travel such far distances?

Monarchs are able to travel such far distances because they fly very efficiently. They take advantage of air currents and actually soar, like many birds do. This takes much less energy than flapping their wings all the time. They choose altitudes at which they can take advantage of the wind to help them on their long migratory flights. And they don't fly when there's a strong wind blowing in the wrong direction. They also store up a lot of energy for these long trips. This energy comes from the food they eat as caterpillars, and also from the nectar they get from flowers.

Can monarchs fly in the rain?

No, at least not for long!

Are monarchs territorial over milkweed?

Male monarchs will patrol the milkweed patches, waiting for females. While doing so they will chase away other males (they have also been observed trying to mate with other males). The twirling chase they do can be seen as aggressive. This behavior is not necessarily 'territorial', but is to help them get a chance to mate.
 

How do monarchs find milkweed?

Monarchs find milkweed using their sense of sight and smell (sensory receptors). They have sensory receptors in their antennae and front legs. Females will 'taste' milkweed with their feet prior to laying eggs on it. Reproductive female monarchs continuously move across the landscape in search of milkweed on which to lay their eggs. For a more detailed response, Journey North has an excellent article on the topic.

What's the difference between a chrysalis and a cocoon?

The words cocoon and chrysalis are often used interchangeably when talking about monarchs and other butterflies. However, they are two completely different things! Cocoons are specific to moths, while chrysalises are formed by butterflies. Moths spin silk around themselves and molt inside the silk casing. This provides extra warmth and protection from the surrounding environment. You can usually find cocoons attached to the side of something or buried underground or in leaf litter. 

Chrysalises, on the other hand, are not silk. Butterflies molt into a chrysalis, which is a hard exoskeleton covering that protects the developing butterfly beneath. Chrysalises are typicall found hanging from something. For example, monarchs spin a small silk button from which to hang upsidedown before molting from head to abdomen! 

How do monarchs fly? Why do I see them sitting with their wings open?

Monarchs are gliders - they do not rapidly flap their wings like many other flying insects. Instead, they flap their wings a few time, and ride on columns of thermal (warm) air. Because of this, they're able to fly very high. They've been reported as high as 1,250 meters, or 3/4 of a mile above the Earth's surface!

You could be seeing monarchs sitting with their wings open for a couple of reasons. For monarchs to fly, it needs to be at least 55 degrees Fahrenheit. Sometimes monarchs will sit with their wings open to heat up their flight muscles. It's also very hard for monarchs to fly with wet wings. If a monarch gets wet in the rain, they may sit and dry their wings.

Do monarchs sleep?

It depends what you consider sleep! Monarchs are active during the day, or diurnal, and they rest at night or when it is cool in trees, shrubs or other sheltered areas. This state of rest in most insects is called torpor. They do not have eyelids, so they rest with their eyes open. Monarchs are also unable to fly if it is below 55 degrees Fahrenheit.

Does it hurt monarchs to touch their wings?

Gentle handling of monarchs to test for OE or tag, for example, is relatively harmless. Some wing scales are removed with handling, so it is important to minimize the amount you handle a butterfly to reduce the risk of damaging the wings. To hold a monarch butterfly safely, use your thumb and forefinger to firmly grasp all four of it's wings. For instructions on OE sampling, visit Project Monarch Health's website. For instructions on monarch tagging, visit Monarch Watch's website.

How far can monarchs fly?

Every fall, North American monarchs fly south to spend the winter at roosting sites in Central Mexico or along the Pacific Coast. Monarchs are the only butterflies to make such a long, two-way migration. Eastern monarchs may fly up to 3000 miles in the fall to reach their winter destination if they are coming from the far northern part of the eastern breeding range. If they are coming from a more southern area of the breeding range, they will have fewer miles to go.

Less is known about the timing and location of breeding and migratory movement in the western U.S. Usually, monarchs coming from west of the Rockies make a shorter journey to the coast of California. In some cases, western monarchs have been documented to fly long distances to Mexico rather than to closer sites in California!

During migration, monarchs will fly about 25-30 miles per day in general. When weather conditions are favorable, they may be able to go further, but poor weather conditions may also prevent them from traveling at all! Many factors influence how far monarchs can travel in one day, so it is quite variable.

You can help document the migration of monarchs wherever you live by contributing to monarch community science!

To learn more about monarch migration, visit our migration page, Journey North, or the Southwest Monarch Study.

How many legs do monarchs have?

It sometimes looks like adult monarchs only have 4 legs, and that caterpillars have a lot more. However, all insects, including monarchs actually have 6 legs. Adult monarchs hold their front two legs close up to their bodies most of the time, and can even use these two front legs to taste-test milkweed before laying eggs on it! Monarch caterpillars have have 6 true legs (3 sets) and 10 prolegs or false legs (5 sets). 

What do monarchs eat?

In North America, monarch caterpillars rely on milkweed (Asclepias genus) and a few closely related genera to grow and develop. Female monarchs use a series of cues to find milkweed and lay their eggs on the leaves of this plant.  After the egg hatches, the caterpillar feeds on milkweed exclusively, and does not leave the host plant until it is ready to pupate. Therefore, milkweed is known as the “host plant” for monarchs. Adult monarchs drink the nectar of many species of flowering plants. It is important for monarch habitat to provide food sources for both caterpillars and adult butterflies, so plant native milkweed and nectar flowers in your habitat! 

Do monarchs return to the same areas when they are traveling north?

There is no evidence to suggest that an individual monarch’s offspring return annually to the habitats their ancestors came from. It is most likely that the monarchs you see each year are new to your garden, and not the same monarchs that grew there previously, or their descendants. This is because there are 4 generations that take place throughout the year for eastern monarchs. By the time monarchs are back in the summer breeding range the next year, they are generations removed from the breeding individuals of the previous year. 

During the eastern population’s summer breeding season, 3 generations pass before the migratory generation (the 4th generation) leaves for Mexico. Successful migrating monarchs will live between 6 to 9 months and reproduce and die in the southern U.S. in the spring. Their offspring then carry on their migration north. Therefore, individual monarchs do not make it back to their original starting place. For a visual reference of the monarch generations click here.