August 1, 2008 Structural engineers created a cocoon-like structure to hold butterflies and keep them flying around visitors. Low ceilings keep the insects at visitor-level, while screened-off ventilation systems and rounded corners protect butterflies from potential dangers. Environmental controls maintain a flutter-friendly 80 degree, 80 percent humidity permanent summer's day.
Inside a butterfly house, you can get an up close look at these delicate creatures. There are many challenges when it comes to designing a home just for butterflies.
One butterfly house, at the Smithsonian Institution in Washington, D.C. holds some of the world's most beautiful butterflies. But building a home for butterflies to live year-round had its challenges.
"Basically, we wanted, or needed to create an outdoor environment in an indoor space," says structural engineer Stephanie Cheng.
Structural engineers and entomologists joined forces and designed a cocoon-like structure with special features like low ceilings to keep butterflies down around visitor level. "We wanted to make it an experience where the butterflies were actually flying around you," Cheng explains.
Large screens prevent butterflies from getting sucked into ventilation systems that maintain perfect heat and humidity. Also, there are no right angles where insects can get trapped.
"Whereas with a curve they just kind of bounce off of it and don't get struck which is one thing we wanted to prevent," says Nate Erwin, exhibit manager at the Smithsonian Institution.
The civil engineering behind the design may go unnoticed by visitors, but it helped build a happy home for the butterfly's that call it home.
"So far the reaction to visitors here at the museum to our butterfly pavilion is just really positive, many visitors don't get a chance to see butterflies up close that often," Erwin says.
A perfect place to visit and watch nature come alive.
ABOUT METAMORPHOSIS: Butterflies change into very different forms as they grow, due to a process called metamorphosis. It begins when a butterfly lays an egg on the bottom of a leaf near the top of the host plant. The eggs hatch a few days later, then go through three stages: larva (caterpillar), pupa (when the larva hibernates in a sac), and adult. Monarch butterflies go through the entire process in about three months, but some species of butterfly can take as long as several years to go from the egg to adult stage.
HOW DO HUMANS SEE COLORS? The human eye works in much the same way as a camera captures images on film. Its "film" is the retina, a thin layer of neural tissue lining the back of the eye, made of photoreceptor cells that receive light, and other cells that interpret this information and send the signal to the brain via the optic nerve. The retina contains two kinds of photoreceptor cells: cone cells and rod cells. Cone cells are sensitive to bright light and can perceive colors. The human eye has three types of cone cells, each sensitive to a particular primary color of light: blue, green and red. These three primary colors can mix in the eye so we can see more complex shades, such as violet or orange. Objects absorb some colors of light and reflect others, and this determines the colors that we see. When light hits a bright red apple, for instance, the appleýs surface absorbs all the wavelengths except red, which is reflected to the eye. So we perceive the apple as being red. In contrast, rod cells work best in low light and can perceive black and white images.
The American Society of Civil Engineers contributed to the information contained in the TV portion of this report.