Natural History Magazine

nature.net

June 2008

Butterfly Effect

By Robert Anderson

Several years ago, while walking through the hills of our Los Angeles neighborhood, my son and I were surrounded a swarm of medium-size butterflies, painted orange and black, with white spots on the wingtips. They weren’t flitting from flower to flower; they were fluttering by, twenty or more a minute.

“Pavilion of Wings,” an outdoor exhibit of living butterflies at the Natural History Museum of Los Angeles County, runs until September 1, 2008.

We stood still and watched the river of butterflies flow northward, dodging homes, trees, and us—any obstacle in their way. Back home, I turned to the Web site of the North American Butterfly Association and learned (through their questions and answers section) that we had witnessed a migrating stream of “painted ladies,” the most cosmopolitan of butterfly species, found on all continents except Antarctica.

Worldwide interest in butterflies has spawned a plethora of groups that study the insects. In addition to the North American Butterfly Association, another organization useful to both professional and recreational butterfly enthusiasts is The Lepidopterists’ Society. Click “Lepidoptera Information” to show a submenu that includes identification aids, frequently asked questions, and other useful subjects such as the Society’s policy on collecting specimens, which they encourage as long as strict guidelines are followed. With roughly 165,000 species of butterflies and moths worldwide, identifying one via the Internet is not always easy, particularly when the majority are not yet photographed and listed on the Web. The Society lists two sites for help in identifying moths and one for their more colorful cousins: Butterflies and Moths of North America. This site has a database of more than 2,800 Lepidoptera, with dynamic distribution maps, photos of adults and caterpillars, life histories, habitat, and conservation and management concerns. You can search the database by taxonomic group, species name, or by your local area map; or browse the image gallery by Family. The Big Sky Institute at Montana State University has a Children’s Butterfly Site with basic information, as well as a great list of links to explore.

Intrigued by the painted lady migration I witnessed, I found several sites with more information on butterfly flight. Monarch Watch at the Kansas Biological Survey, University of Kansas, is devoted to nature’s preeminent butterfly traveler. Click “Migration and Tagging” to learn more about these beautiful insects that fly as far as three thousand miles to reach their wintering spots. How do monarchs find the overwintering sites each year? “Somehow they know their way, even though the butterflies returning to Mexico or California each fall are the great-great-grandchildren of the butterflies that left the previous spring. No one knows exactly how their homing system works; it is another of the many unanswered questions in the butterfly world.” This site encourages citizen scientists, including children, to participate in their tagging program to help understand the migration. Elsewhere, I found a paper on how scientists are using radar to track butterflies: see Tracking butterfly flight paths across the landscape with harmonic radar.

Other sites focus on the butterfly’s seemingly chaotic flight path—even when migrating. On its site Flow visualization of butterfly aerodynamic mechanisms, the Insect Flight Group at Oxford describes how the butterfly’s beating wings disturb the air moving past. The researchers include a video clip of a red admiral butterfly to illustrate the flow. The Z. Jane Wang Research Group

Photograph of a butterfly-type ornithopter developed by researchers at the University of Tokyo to investigate butterfly flight

in the Department of Theoretical and Applied Mechanics at Cornell University has studied flight in several insects including dragonflies. “In the News” lists several links to articles on insect flight.

In “Flight Dynamics of a Butterfly-type Ornithopter (PDF)” researchers at the University of Tokyo describe a mechanical model they used to learn that the insect’s motion mitigates the effects of the vortices created in the air by each wing beat. Sheri L. Anderson at Colorado State University in Fort Collins describes how flight patterns vary in accordance with how tasty they are to predators; see “Butterfly flight patterns: How flight and color attribute to palatability.”

Lepidopterans’ many generations over a relatively short period of time offer us a chance to observe evolution in progress. Peppered moths near Manchester England, for example, gradually darkened as predators pick off the paler moths that vainly seek camouflage in the soot-covered industrial area. See Peppered moth evolution for a more detailed account of the pepper moth saga. Here are two more recent examples, both from BBC News: “Butterfly Unlocks Evolution Secret” and “Butterfly shows evolution at work.” According to the University of California Museum of Paleontology in Berkeley, the first butterflies appeared in conjunction with the spread of flowering plants in the lower Cretaceous. “Primitive lepidopterans retain functional chewing mouthparts as adults, but more derived ones have partially or completely lost the mandibles and developed a long proboscis for drinking nectar from flowers.”

While butterflies in their adult stage have developed a symbiotic pollination-for-nectar arrangement with plants, many caterpillars have evolved tradeoffs with ants. Watch this National Geographic video to see how one species pays ants with its own sweet body secretions in exchange for protection. (This video is followed by three others, on natural moth control, monarch butterfly habitat destruction, and the nature of swarms, including those of the monarch.) For more on the caterpillars’ remarkable symbiosis read “Myrmecophily: Ants and Butterflies, The Evolution, Effects, and Maintenance of their Relationships,” a student review article by Jay Mann at Colorado State University in Fort Collins.

Robert Anderson is a freelance science writer who lives in Los Angeles.

If you admire the brilliant, sometimes metallic, colors of butterflies’ wings, go to Bugbios to learn how the wing scales of six different species (including painted ladies) make striking art. Christina Brodie in the United Kingdom, on her page Geometry and Pattern in Nature 2: Iridescence in butterfly wing scales, provides more information on how the scales produce such vivid colors.

I try to avoid commercial Web sites, but if you really want to appreciate the variety of wild patterns found on the butterfly’s wing, go to Butterfly Alphabet. Created by photographer Kjell Sandved, the Web page shows that all letters and numbers can be found if your look on the wings of enough butterflies.

Finally, get out and see some live butterflies. The Butterfly Garden Website will tell you what kind of plants will help attract butterflies in your area. Sue’s Butterfly Haven has an extensive, state-by-state list of butterfly gardens, live museum exhibits, and festivals. For instance, near me I found the Pavilion of Wings at the Natural History Museum of Los Angeles, an outdoor exhibit with more than thirty live species—including the California dogface, the state butterfly.

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