The KING of Butterflies – The MONARCH

(Danaus plexippus: Greek for – Sleepy Tranformation)

Male Monarch Female Monarch
Fig. 1 Fig. 2

Monarch butterflies are the most beautiful of all butterflies and are considered the “KING” of the butterflies, hence the name “Monarch”. There are lots of very cool things to learn about the monarch butterfly and we’ll try to get through most of them here.

Many have wondered, — what is the obvious telltale difference between a Male and a Female Monarch?  The most prominent sign, are 2 black circular markings on the lower inner wings.  See Fig.1 above and note where the arrow is pointing.  Another, not so obvious, factor is the differences in their abdomens.  Females have a notch at the tail end of their abdomens, the males do not. The rest of their anatomy is the same including the stained glass markings on their wings.

Why are Monarchs so important?  Several reasons:

  1. They are great pollinators as they travel the continent.
  2. Scientifically, Monarchs have been used, for centuries, to investigate many areas of biological research in fields of navigation, pest control, embryology, mimicry, evolution, genetics, population dynamics and biodiversity conservation.
  3. Monarchs, as well as other butterflies, are great indicators of a healthy environment and stable ecosystem. 
  4. They are a part of our heritage.
  5. People enjoy seeing Monarchs in their homes and in the countryside.
  6. They are intrinsically valuable and worthy of conservation in their own right.

The Monarch cycles through 4 generations.  It is the 4th generation that begins the 1st generation and is the most unique generation out of all the other 3 generations.

This 4th generation of Monarchs was born in the Fall of the northern parts of the United States and southern parts of Canada.  Their main purpose before overwintering (hibernation) is to drink from the nectar of many plants in order to endure the long journey south where they will overwinter for 4-5 months.

There are some fascinating and unique factors about the 4th generation of Monarchs.

  1. They will live about 8 months whereas the other 3 generations only live 2 to 6 weeks.
  2. The 4th generation is not sexually active or ready until after their migration south and not until after they have overwintered; whereas, the other 3 generations are ready 4-5 days after birth.
  3. Another unique factor is that the 4th generation of Monarchs do not reproduce right away whereas the other 3 generation start reproducing 2 weeks after birth.  It is not until the 4rth generation has begun migrating after overwintering, (some 6-8 months after they are born) that they begin to reproduce.
  4. Lastly, and the most unique and mysterious factor of the 4rth generations of Monarchs is their ability to migrate south having never flown the trek to and from beforehand. Monarchs cannot tolerate cold climates and fly to warmer regions of the Untied States.  Most go to southern  Mexico, and those in the upper western region of the United States fly to the west coast of California.  This flight begins September, October, and November, starting with southern Canada first. Adversely, Monarchs cannot tolerate hot dry weather and therefore migrate northeast or  north to cooler climates

The 4 Generations

We need to start with the 4th generation.  Once the 4rth generation of Monarchs fly south, they will enter their overwintering phase for 4 to 5 months. After overwintering ends, they will awake, find water, mate, and then begin flying north to find food (nectar), mate (if not already done earlier) and lay eggs.  When Monarchs mate, the male latches onto the female for hours, sometimes up to a full day, Fig.6.  They continue their trek north to the southern parts of the United States. Those in California will fly easterly remaining on the western parts of the continent.

Once they arrive in the southern states or the mid western states, they will lay hundreds of eggs in groupings on the underside of Milkweed leaves, Fig. 9.  This begins the 1st generation of Monarchs.  Note their migratory patterns in Fig. 3, Fig. 4, and Fig.5, below.

4th generation lays eggs 1st generation is born and fly north

Fig. 3



Total US Monarch Migration Monarchs Mating

Fig. 5

Generation 1: (late April to early June)

The children of the previous 4th generation.

The 4th generation begins the 1st generation. After a long 4-5 month period of overwintering, the 4th generation awakes, and the first thing it does is find water!!  Afterwards, it mates.  The males literally pluck the females off the leaves and join together in a mating ritual that can last up to a day, Fig.6.  The monarchs then fly north, heading to a place they’ve never been.  Their only map imprinted upon their genes.  A great video released by National Geographic can be visited at this link:  Great Migrations.

Along the way they find nectar and continue to mate.  They then begin the task of laying eggs while heading north. This marks the 1st generation. The Monarch lay eggs on only one kind of plant, Fig.9.  The Asclepias, commonly known as the Milkweed, Fig.7 and Fig.8.  The reason being is because the resulting caterpillar only eats the leaves from Milkweeds whereas the adult butterfly will drink from the nectar on the flowering portions of milkweed and other plants. There are a few varieties of this genus family.  A listing of various milkweed plants can be found at this link: Wikipedia: Asclepias.  Below are just 2 of the many varieties found in the US, Fig.7 and Fig.8.

The monarch butterfly is such a beautiful flying insect that one would not think it poisonous!   The bright colors on its body are so clearly visible that we feel they can easily attract the predators, but in contrast, this color helps the predators to distinguish the Monarchs from the other butterflies. It is because of the Monarch’s lovely vibrant orange appearance, that predators avoid eating them. The poison stored in the Monarchs wings is acquired from the poison toxins found the milkweed leaves called cardiac glycosides.  Studies say, the foul taste of Monarch keeps the predators away and the bright color is a warning to the predators about the poisonous characteristic of Monarchs

Asclepias Tuberosa Asclepias Ordefolia

Fig. 7
..Fig. 8

The life cycle of the butterfly is in 4 stages.

First Stage: The Egg. This is a protected hard shell called the Chorion.  The inside of the shell is lined with a layer of wax to keep the shell from drying out.  The eggs are laid on the underside of the Milkweed leaves very close together, Fig.9.  As females lay their eggs, they secrete a small amount of glue to keep their eggs attached to the leaves. Monarch can lay 330-500 eggs over 2 to 5 weeks.

Second Stage:  The Larva:  In about 4 to 5 days, the eggs hatch out to a caterpillar, Fig.10.  It’s first meal is the shell it came from.  From that time on the baby caterpillar doesn’t do much but eat the leaves of the milkweed plant in order to grow.

First Stage:  The Egg Second Stage:  The Larva (Caterpillar)
Fig. 9 Fig. 10

Larvae parts: Fig. 11

  • 3 body parts: the head, thorax, and abdomen.
  • Head: the has a pair of short antennae, mouthparts and 6 pairs of simple eyes.
  • Antennae: help to guide the caterpillar around.
  • Mouthparts: has 3 parts, upper lip, mandible, and lower lip.
  • Maxillary palps:  sensory organs that help direct food to it’s mouth
  • Spinneret:  used to create silk to anchor the caterpillar when needed.
  • Spiracles:  holes in the sides of their thorax and abdomen through which oxygen is transported to their air tubes.
  • Tracheae:  air tubes that carry oxygen throughout the body.
  • Legs: Prolegs and true legs
Life Stages and Anatomy of the Monarch
Fig. 11

The head capsule is the first part of the old skin to come off during the molting process. Then the old skin peels back from the front of the caterpillar. At first, the new skin is very soft, and provides little support or protection. This new skin soon hardens and molds itself to the caterpillar.

The shed skin is often eaten before the caterpillar ingests more plant food! The intervals between molts are called instars. To learn more about the caterpillars instars, visit the Minnesota University at this link:  Monarch Life Cycle

Milkweed is highly poisonous to grazing animals and humans if ingested.  After about 2 weeks, they find a place to attach themselves to and begin the process of metamorphosis. It attaches itself to a stem or leaf using a silk strand.  It hangs itself in a “J” form and then begins to cocoon itself in a protein shell called the Pupa (Chrysalis).

Stage 3:  The Pupa (Chrysalis). 18 days to 2 weeks, Fig. 12.   This is where the caterpillar undergoes a remarkable transformation via metamorphosis.  The process begins with creating a silky glue to the underside of a firm branch.  The  caterpillar makes a ‘U’ turn on the branch in order to insert it’s rear end claspers  into the silky substance and then hangs upside down in a “J” position.  The first part of the Chrysalis begins at the back of it’s head.  The skin splits and the substance that creates the shell, emerges.  At first, the shell of the pupa is soft but within a few hours it hardens. The green color camouflages it from predators.  Inside the mouth changes over to a straw like form and the body begins to grow wings.

 The 4 stages of Monarch metamorphosis
Fig. 12

Metamorphosis: So, just what is happening inside the pupa as the caterpillar undergoes it’s miraculous transformation?

  1. Inside the caterpillar itself, enzymes are at the ready as well as particular cells, called the “Imaginal disks” .  After the last (5th molt), these cells are tuned on.
  2. Enzymes are released that actually digest the caterpillar tissue.  This forms a rich medium for the new growth.
  3. The imagining disks cells have specific functions.  Like a human body, the heart cells grow into heart cells, the brain into the brain and so on.  The caterpillar disks have wing cells that grow into wings, antennae cells that grow into antennae and so on.

Nothing like this transformation happens in vertebrates such as ourselves.  It’s a phenomenon of insects and it truly is a miraculous biological process of transformation.  It’s like rebuilding your Toyota car into a Cadillac!

Stage 4: Monarch Butterfly!  Finally, the shell bursts open and a butterfly emerges, Fig13. It takes a couple of hours before it can fly because its wings are tiny, wet and wrinkly. The butterfly pumps body fluid, called hemolymph, into the wings to make them grow big and strong. After the wings have hardened, it’s time to sip fluids! The butterfly flies off in search of its first meal, which it will slurp up through its straw-like tongue, or proboscis. After just dining on milkweed, butterflies enjoy a little more variety and take their nectar from several differing flowers, making them one of nature’s major migratory pollinators.

The Monarch is born!!
.Fig. 13

Generation 1 Monarchs have migrated half or more of the continent lay eggs along the way.  They can reproduce as soon as 4-5 days after birth. These eggs will become the 2nd generation of Monarchs. 

Generation 2: (June to July)

The grandchildren of the previous 4th generation.

Generation 2 adult Monarchs emerge in June and July, mate and lay eggs soon after emerging. Most of those that begin their lives in the south move north as adults, since the southern summers are too hot and dry for their offspring. Those laid farther north probably do not move far, and can use all of their energy to produce as many offspring as possible.  

Note the migratory patterns of Generation 2, Fig. 14 and Fig. 15 below.  As noted above, those in the western part of the continent will migrate easterly to the upper left near the Rocky Mountains. 


Fig. 14
.Fig. 15

The life span of a generation 2 Monarch ranges between 2 weeks to 6.  Their main purpose is drink nectar, mate, and lay eggs.  The eggs from this generation create generation 3. 

Generation 3: (July to August)

The Great Grandchildren of the previous 4th generation.

Generation 3 adult Monarchs emerge in July to August.  Once born, they will either remain where they are or fly further north or northeast depending on their current location. The life span of generation 3 is also 2 weeks to 6.   Like it’s generation before them, their main purpose is to drink nectar, mate, and lay eggs.  These eggs hatch into the last and most astonishing generation of all — generation 4, also called the Super Generation.  

Generation 4, the Super Generation: (August to September)

The Great Great Grandchildren to the previous 4th generation.

The 4th successive generation is born August to September.  It is this generation that is the most fascinating of all. 

The annual migration of North America’s Monarch butterflies is one of the greatest spectacles of nature. Each year, more than 300 million Monarchs travel more than 2,000 miles from Northern America and Canada to a remote forest 200 miles west of Mexico city.  But they are as fragile as they are beautiful.  Sudden changes in their environment can mean disaster.  A January 2002 rain storm followed with freezing temperatures claimed as many as 250 million, almost 80 percent of the population at the El Resario Butterfly Sanctuary, just one of a half dozen sanctuaries in the area. Their bodies covered the forest floor giving off an unusual odor. Biologists suspect logging to have contributed to the kill-off opening the forest to wind and cold air.  In the last few decades nearly half of the woods that the Monarchs depend upon in this region have been destroyed, primarily by illegal logging. The Mexican government along with the World Log Life Fund has launched efforts to preserve what is left by offering to pay land owners to not cut trees.   But the money is very limited. The 2002 storm was not the first to strike the Monarch population nor will it likely be the last. For the moment, millions of the Monarch butterflies still take to the skies each year. 

The 4th generation is the only generation that does not die off in 2 to 6 weeks.  This generation will need to last 8 months so that they can migrate south, overwinter 4-5 months, and then migrate north to the southern parts of the continent to lay eggs, —  then they die off. How does this occur?

These unique and amazing creatures always return to the same trees as the fourth generation before them without ever being there before.  How is this possible? 

Theories on Migration: (September, October, and November)

  1. Many scientists speculate that they must have an internal map and compass that is innate.  At the very least they are born with an instinct to complete the migration.
  2. The Monarch butterfly uses the position of the sun as a compass.  They migrate during the day, and the sun is the celestial cue that leads them south.
  3. The Monarchs have an internal clock that helps them orient themselves to head south depending on the position of the sun.
  4. The Monarch butterfly has a magnetic compass that gives them a keen sense of direction.  This magnetic compass helps direct them to the equator.
  5. Once they are far enough south, they use smell and social cues to help guide them to their exact wintering sites. 
  6. It is also theorized that Monarchs are born with an internal map based on the magnetic field of the Earth that guides them to all of their destinations.  This is much like sea turtles.  The creatures are born with an internal map that directs them to the places they need to go in order to survive. 

Summary of Migrations and  Generations: 

Monarch’s Annual Cycle

Diapause, repressed mating, food storage for migration, temperature regulations, wing size. Each 

Gliding, thermal air, speeds  15-25mph, tagged-265 miles per day, 3,000 mile journey,  fat 140mg-flap 44hrs, soaring and gliding 1,060hrs

Magnetic compass, light, ultraviolet

Circular pic of generations


Other Types of Monarchs

White Monarch

Monarch the official insect of 7 states

Milkweed & Pests

Under Construction

To be continued……


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