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Frequently Asked Questions

1. How much does a Monarch weigh?
Monarchs range in mass from .25 to .75 grams (a dime has a mass of 2.3 grams). Males are usually larger than females, with average masses of .56 vs .53 grams respectively. (A good classroom question: why are males larger in both mass and wing length than females?) [Back to FAQs]

2. How much does a Monarch egg weigh?
A single Monarch egg has a mass of only 0.46 mg (0.00046 g), but after feeding for 15 days, a mature 5th instar (5th stage) larva can reach a mass of 1.5 g - that's 3,261 times heavier than an egg! The average pupa is 1.2 g, which represents a loss of 20% of the larval mass, but the mature adult is only 0.5 g, only 58% of pupal mass. (A good classroom question: why does the adult weigh less than the larva and pupa? What accounts for the loss in mass?) [Back to FAQs]

3. How fast does the migration advance?
In the midwest, we have observed that 5-6 days after masses of Monarchs assemble in Minneapolis/St. Paul (late August) the front of the migration reaches Des Moines, Iowa (4-6 Sept.) - a distance of 240 miles (360 km). It takes another 5-6 days for this wave, or front, to reach Lawrence, Kansas (usually 9-10 Sept.) - another 220 miles (330 km). However, from Lawrence, KS to Austin, TX a distance of 700 miles (1050 km), the interval varies from 6-14 days. The first masses of Monarchs usually reach the Texas/Mexico border (Eagle Pass, etc.) in the last days of September. In the midwest, if we assume the migration starts in NW Minnesota, the distance to the border is 1500 miles (2250 km). Therefore, the migration advances at roughly 50 miles (75 km) per day (1500/30 migrating days from 28 Aug. to 28 Sept.). However, these are averages, and there are reports from recoveries of tagged Monarchs which indicate flight distances up to 129 km a day. [Back to FAQs]

4. How fast do individual migrating Monarchs fly?
Clearly, the flight speed of such a small organism depends on environmental such as wind speed and direction relative to the heading (direction) of the butterfly. Monarchs are slow fliers relative to other butterflies and moths, flapping their wings only 5-12 times per second. Their flight speeds have been measured at 5 meters per second, 18 km or 12 miles per hour; but, if disturbed, they can fly much faster for short distances. Surprisingly, there are few data on flight speeds of Monarchs and other butterflies. This could be a good project. All that is required is an open field, a clipboard, a tape measure, a stop watch, a wind speed and direction indicator and some keen observers. [Back to FAQs]

5. Do Monarchs occur outside of North America?
Yes. Monarchs are found at middle elevations in many places in central and south America. Although not well studied in these areas, there are some indications that Monarchs migrate to dryer areas when the wet season begins and then back to wetter areas when the dry season becomes so severe the host plants die back. In the last century Monarchs were introduced, evidently by ship traffic, to the Azores, Australia, New Zealand, Hawaii and many Pacific islands. More recently a limited population of Monarchs has become established in southern Spain. [Back to FAQs]

6. How long do adult Monarchs live?
In captivity, reproductively active Monarchs can live up to 6 weeks - if they are well cared for. In the wild, the duration of the life span depends on the time of year. Summer Monarchs, which are reproductively active, probably live 2-6 weeks. The survivorship of summer Monarchs probably declines when nectar is scarce and when temperatures exceed 95 F (35 C). Generally insects live "faster" and have shorter lifespans when it is hot and dry. Monarchs which overwinter in Mexico can live up to 8 months! These Monarchs are in diapause and are not reproductively active until the end of the winter in Mexico. The cool conditions at the roost sites in Mexico, the inactivity of the butterflies and the lower metabolism during diapause, contribute to the longer lifespan of the migratory generation. [Back to FAQs]

7. Do Monarchs that migrate to Mexico in the fall make the trip back to the area from which they started?
After clustering in the roosts in Mexico for 5 months in the winter, Monarchs begin to make their way back north. Before leaving the roosts, they become sexually active and mate multiple times. As the female Monarchs move northward, they lay eggs on milkweed plants along their flightway. Most of the northward migrants complete their reproduction in the southern states, but each spring relatively small numbers return to the Midwest, sometimes as far north as southern Iowa. However, very few if any, reach the area from which they originated. It is generally believed that Monarchs maturing from the first eggs laid on milkweeds in the southern states in late March and early April continue the migration northward in May, eventually reaching the northern limits of the breeding grounds in central and eastern Canada. After 2-3 summer generations, Monarchs will again migrate to their winter roosts in the fall without having any previous experience with locating the roosts or "knowing" where the roosts are. How do they do this?! This is one of the mysteries of the Monarchs. [Back to FAQs]

8. Why do Monarchs have only 4 legs?
Monarchs actually have 6 legs like all other insects, but their two front legs are very tiny and folded up so that you cannot see them. [Back to FAQs]

9. What are those things sticking out of the head and tail of Monarch caterpillars? Are they antennae?
The black filaments, sometimes called tentacles, protruding from behind the head and near the end of the abdomen of the larvae are not antennae, but may serve some tactile function such as alerting the larvae when they are close to an object. Also, it seems that the filaments respond to sound; try clapping your hands or playing some music with heavy bass, and the caterpillar's filaments will "jerk" in response to the sound. Does this mean that caterpillars "hear" with these structures? Probably not, but it might be fun to do some experiments to determine how and why those caterpillars "dance" to the music. The caterpillars do have antennae that are located on the head, but they are very small and inconspicuous. [Back to FAQs]

10. Where did the Monarch get its name?
Early settlers who came to North America from Europe, particularly those from Holland and England, were impressed by the sight of the Monarch butterfly. So, they named it "Monarch," after King William, Prince of Orange, stateholder of Holland, and later named King of England. The monarchs' color suggested the name. From William, we get the vernacular "Billy", and hence the name "King Billy", which has also been applied to the butterfly. [Back to FAQs]

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