Saturday, September 17, 2011

The King of Butterflies

Image by Tim Hamilton via Flickr

It's been since July that we've taken a look at a butterfly so we're long overdue. We all know this beauty. The king of butterflies, as it's been called, the monarch. Or The Monarch, Danaus plexippus. The Monarch Butterfly was discovered and named in 1874 by Samuel H. Scudder and has become widely known for its incredible migration. But it isn't that simple, of course.

Image via Monarch Watch

Not all Monarchs fly to Mexico and no single monarch makes the round trip. Some make the trip and get halfway back before dying. Monarchs being their migration south in the fall, beginning in September and October (they're on their way!). Those east of the Rockies overwinter in high elevation mountains in southern Mexico. Those on the western side of the Rockies migrate to southern California, in the Pacific Grove area and there are even some overwintering sites in southern Florida.

To complicate things further, not all monarch butterflies migrate. It's complicated. But not. Stick with me. Each year there are four generations of monarchs. A generation consists of the egg, the larva, the pupae, and the adult. Once the adult lays her eggs, she dies and the next generation commences.

The egg stage lasts 3-4 days and is therefore the shortest stage in the life cycle, barring anything unfortunate. Once hatched, the monarch begins the larval stage by eating it's egg case, which is full of vitamins and yummy things, and then moves on to consume its host plant, the milkweed. It is a caterpillar and monarch caterpillars eat only milkweed. And they eat tons of it. This larval stage is further divided into what is called an instar. Caterpillars grow very quickly and soon outgrow their own skin. We do the same but just get stretch marks. The caterpillar molts, or sheds its tight, striped suit for a newer, more roomy skin and will generally eat the skin it just shed for more delicious butterfly nutrients. There are five instars. This stage lasts 10-14 days, after which it pupates and forms a chrysalis.

Image via How Stuff Works

A monarch pupae is a thing of beauty. The caterpillar twists around and anchors its rear to a secure, protected surface and begins its final molt. But this time a caterpillar does not emerge- it is the pupae.

Image via Science Photo Library

At first the pupae doesn't look like anything, really. The caterpillar's skin splits to reveal a green sac of ... something. But look closer ...

New pupae. After about an hour, the pupa will reshape into the classic chrysalis form.
Image via Shady Oak Butterfly Farm

... it shows signs of the life to come. It is still a bit of a mystery regarding what actually goes on inside the chrysalis. Polite society says "the caterpillar re-structures itself," or "re-organizes".  In fact, and I'll just say it with apologies to my squeamish readers, the caterpillar turns to mush. It under goes metamorphosis- a complete transformation. It is very vulnerable during this early pupal stage so if you happen upon one, please don't touch it or move it. Skilled lepidopterists can sometimes "thread" a fallen pupae and hang it again but that's a tricky thing to try. Just leave the pupae or chrysalis as you find it. Nature is a cruel thing sometimes and only about 2 out of 100 eggs actually become butterflies.

A gentleman named Clay Ruth has some really neat and informative videos of a caterpillar pupating and contracting. Click here and scroll down toward to bottom of the page for the links.

Image Source

The function of the gold spots on the chrysalis are another mystery though the two we see in the middle of the photo above will be over the eyes of the adult butterfly. Pupae do not see. These spots are actually refracted light from the layers of the pupae. But did you know, that in addition to being able to see hints of the adult butterfly on the chrysalis, you can also determine the gender of the butterfly that will emerge? Oh it's cool.

Image via Monarch Watch

In the image above, the chrysalis is turned so that the cremaster, from which it hangs, is on the left. At the top of the chrysalis (seen here on the right) are a series of abdominal rings and a row of matched dots. Below the last row you can see a small crease on the abdominal ring. The butterfly that will eclose from this chrysalis will be a female. Males do not have this crease. How cool is that?

Image via The Inside Story

Immediately before the adult emerges, the chrysalis will become clear.

So finally, the adult emerges. And ain't she a beauty. Or he? Now how do we tell the difference? In many species, butterflies, birds, whatever, the females are more dull in coloration and markings or are larger in size. Not so the monarch. Both are equally marked and colored- loud and proud. So ...

Image via Monarch Watch

Male monarchs had thinner vein markings and, more easily seen, a small black dot on each hind wing. This dot is actually composed of special cells that produce pheromones to attract the ladies.

OK- that's one generation. Now let's get back to the migration. In the spring, overwintering monarchs become more active, their circadian and biological clocks teased into action by warmer temperatures, longer daylight, and the position on the sun. Those in California begin to disperse on the western side of the Rockies. Those in Mexico begin their journey northward. At some point, about halfway or so, these butterflies will stop to mate and lay eggs. End of generation one. Generation two, once hatched, will continue northward and will eventually produce the third generation. Adults of generations one through three live from two to six weeks but the fourth generation is special. This 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). Blame it on hormones, because that's what it is, but lower hormone levels cause the butterflies to live longer. This flight will live upwards of eight to nine months and is the generation that will make the trip south. As fall approaches, the lepidopterian clock makes a tick and the butterflies begin to get a hankering for Mexican food. Fourth generation monarchs have been shown to have higher levels of magnetic materials in their bodies. The Transvolcanic Mountain Range in Mexico, which hosts most overwintering sites, has high levels of magnetic anomalies and this geomagnetic mumbo-jumbo may be one way monarchs are able to find their way to their centuries old overwintering sites, even though they've never made the trip before. That plus the solar-powered circadian clocks, the sun's position, and some good old-fashioned divine miracle dust get our friends to their Mexican retreat where they literally hang out for the winter.

Image via Denver Botanic Gardens

Monarchs don't actually hibernate. They are calm and still in the cooler but frost-free climate of the southern Mexico mountain range but do flutter about on sunny days to find water. They do not feed while overwintering but live on the stores of fat they have built up.

Image via World Heritage Convention/UNESCO

The Monarch Butterfly Biosphere Reserve in the Oyamel Forest has been named a World Heritage Site by UNESCO and contains over half of the overwintering sites of the eastern migrating monarchs and receives between 60 million and 1 billion butterflies as year. Oyamel Forest was not confirmed at the destination of migrating monarchs until the 1970s.

The Biosphere is a conservation area. Monarch numbers to the area have been slowly declining. The threat to monarch populations comes from loss of habit (here in the United States at a rate of 6,000 acres a day), genetically modified crops, increasing use of pesticides and herbicides, and illegal logging in the Oyamel Forest. It is a dangerous thing, patrolling the forest in order to stop illegal logging. Lives have been lost. Meanwhile, the small communities in the area have come to rely heavily on the tourist dollar as more and more people come to see the butterflies in their winter lodgings. This conflict between tourism and logging frequently pits neighbor against neighbor.

The Monarch Watch has tons of information about monarchs and has initiated several educational and conservation programs. These programs include the Monarch Waystation program for providing habitat (you can even become a certified Waystation), research such as Monarch tagging, and butterfly gardening information to name just a couple of the resources available on their site. They have also launched "Bring Back The Monarchs", a program designed to reintroduce 20 species of milkweed as well as native nectar-producing flowers.

White varient Monarch.
Photo by Lisa via Flickr

I love to sit out on the back patio on sunny autumn days and watch for the monarchs. They hurry past in little trains, like a flittering parade, on their way to Mexico.

Image via BBC Radio

I know, this post has been WAY longer than I ever planned for our butterfly visits, which are supposed to be brief little "Hellos" but monarchs are simply incredible creatures and the whole life cycle-migration thing is fascinating. We didn't even talk about milkweed or puddling!

Click on the "Bring Back The Monarchs" logo in the sidebar if you would like to find out how you can help restore natural habitat for the king of butterflies. Thanks for coming by today-- hope it was fun. See ya next time!


  1. This was an extremely interesting post. Thank you so much. Each year my family and I watch the migration through southern Ontario. This year it seemed a little earlier and smaller in quantities, but I do not have anything to back that up just my obervation!

  2. Well you have good observational skills- Monarch populations are indeed fluctuating from year to year but overall in a downward trend. That's so sad. You can help the butterflies by planting food source plants for them. Thanks so much for your comments.