Window on Nature
By Lowell & Kaye Christie, F47246
Butterflies are more than tiny works of art “” they’re fascinating little creatures. So this month we’ll share answers to butterfly questions that we’ve had in the past, and provide answers to other questions we didn’t even think to ask until we began working on this column. If you aren’t amazed by some of this information, you’re either a dedicated butterfly watcher or someone who appreciates the beauty without worrying about the whys and hows. Even so, we think you’ll enjoy reading about them.
There are roughly 20,000 butterfly species fluttering about Earth. Of these, approximately 275 species occur regularly in Canada; 575 species exist in the United States (not including Alaska and Hawaii); and roughly 2,000 species are found in Mexico. Imagine. Mexico is home to 10 percent of the world’s butterfly species.
It is estimated that the average number of butterfly species you are likely to find in any one area of the United States is 100. A bit suspicious, we checked this figure out for our home turf and found the number to be very close. Our county butterfly list in California claims 124 species. It may be better than average, but it’s nowhere near what you’ll find in Florida or the Rio Grande Valley in Texas.
We were surprised to learn that butterflies that survive to adulthood don’t have much of a future. Their average life span is about a month “” if a predator, disease, or a moving vehicle doesn’t get them first. Oddly enough, size seems to make a difference in how long a butterfly survives. Good-sized monarch and mourning cloak species can live up to nine months. On the other end of the spectrum, small butterflies may live a week or less. A case in point is the inch-long spring azure, which lives only a couple of days.
Butterflies have so much to do in very little time, such as ensuring the continuance of the family line. Most female butterflies lay their eggs on a plant used for food by the species. That way the host plant (or at least part of it) can be nibbled by the caterpillar right after it hatches from the egg.
Adult butterflies have their own, quite different, life-support systems. They don’t have lungs, so they breathe through openings in their abdomen called spiracles. What’s more, no matter how hard you look, you won’t find a nose on a butterfly. They smell with their antennae and taste with their feet.
Eating seems pretty strange, too, considering that butterflies do not have teeth or a tongue. They use a proboscis instead. Shaped like a straw, the proboscis allows the butterfly to suck nectar from a flower into its mouth. Then, when it’s finished feeding, the butterfly curls the proboscis up beneath its face.
Butterflies appear in all sizes and colors. The giant swallowtail earned its name with a wingspan that can reach up to 5 inches. That is one big butterfly, unless you’ve traveled to the tropics.
Ever wonder how fast and how high a butterfly can fly? Some species flap at a speed of approximately 30 miles per hour. As far as height, migrating monarchs have been documented flying at an altitude of a kilometer or more. (1 kilometer equals 3,281 feet.)
We were surprised and impressed that the painted lady butterfly beats its wings on all continents except South America and Antarctica. And, wonder of wonders, it’s found on our local butterfly list.
Have you ever spotted a butterfly parked at a small circular hole in a tree? If you thought that it might be sipping tree sap, you’re right. But is such a fragile creature able to make its own hole? The answer is “No.” When you see a tree with parallel rows of neatly drilled holes in the trunk or lower branches, the carpenter was a bird, not a butterfly. It takes a sapsucker, whether yellow-bellied, red-napped, or red-breasted, to do the job. They are also sap feeders, and when they’re gone, the hole they made becomes an open “faucet” used by others with similar tastes, such as butterflies.
Plenty of information is available about the lengthy migration of monarch butterflies, but not all butterflies migrate. So how do they survive the winter? If they’re year-round residents of warm-weather areas, no problem. In areas where temperatures drop below freezing, at least one stage of a butterfly species’ life cycle must be cold-resistant. Most butterflies living in cold climates spend the winter as caterpillars or as pupas. Are you ready for this? Some butterflies even produce glycerol … their own antifreeze.
Still, many butterflies migrate south to escape winter’s chill. Then when spring ushers in warmer weather, the butterflies leave their winter quarters in Mexico or the southern United States to fly north to their summer habitat to repopulate the area. For the most part, the return north is gradual, following the warmer temperatures and availability of food. When food is abundant, the butterflies seem to travel through in hoards.
Like the general public, scientists have been curious to learn how a migrating monarch knows where to go. It has never made the trip before, so it didn’t learn the route from flying with other older and more experienced butterflies. After all, monarchs range across 6 million square miles in North America. Yet, because of their limited life span, only one generation each year migrates south to their overwinter area, often in Mexico.
Scientists know that at least four generations of monarchs are produced each year. The first generation emerges from eggs laid in Mexico and the southern states in early spring. They grow as they eat and cycle from caterpillar to chrysalis and then into an adult butterfly. Then they’re ready to head north. Their speed of movement is controlled by the availability of a particular plant, the milkweed, the only plant on which a female monarch will lay its eggs. Thus, they’ll produce several new generations, with each new generation continuing farther north.
The cycling continues until fall, when a final generation of monarchs, apparently responding to the changing angle of the sun, emerge from their chrysalises and immediately begin flying south, a journey of perhaps two months that no living relatives have ever experienced. Recent research indicates that monarch butterflies are able to use the angle and intensity of sunlight to determine the season, as well as which way they’re headed. This amazing internal clock allows them to navigate thousands of miles until they reach their winter turf. Obviously, this southward migration must be genetically controlled, since none of the migrants can follow the lead of other butterflies that have made the trip before. Amazing, isn’t it?