Though famous for their mid-air hovering during hunting, tiny hummingbirds have another trait that is literally telltale: males of some hummingbird species generate loud sounds with their tail feathers while courting females. Recently, for the first time, the cause of these sounds has been identified. Read more in this news release.
Credit: Anand Varma
Biologist Ken Dial and his team at the University of Montana Flight Laboratory have revealed a lot about the origin of flight. Many findings come with the help of sophisticated equipment, such as wind tunnels, lasers and cameras that can record 1,000 frames per second. But a lot of knowledge comes from keen observation, both inside the lab and out in the field. Find out more in this Science Nation video.
Credit: Science Nation, National Science Foundation
Bats are the only mammals that can fly under their own power. Two Brown University researchers--biologist Sharon Swartz and engineer Kenny Breuer--have teamed up to study the mechanics of bat flight. They set up a special facility that includes a wind tunnel and take high-speed video of bats in flight from multiple angles and high-speed video of the velocity field behind the bats using a technique called particle image velocimetry or PIV. Find out more in this Science Nation video.
Credit: Science Nation, National Science Foundation
University of Chicago researchers recently showed that dry granular materials such as sands, seeds and grains have properties similar to liquid, forming water-like droplets when poured from a given source. In this new experiment, researchers measured nanoscale forces that cause droplet formation using a special co-moving apparatus devised for a high-speed camera that captures images much like a skydiver might photograph a fellow jumper in free fall. Read more in this news release.
Credit: Helge F. Gruetjen*, John R. Royer, Scott R. Waitukaitis, and Heinrich M. Jaeger, The University of Chicago
Try this at home: If fruit flies are buzzing around your kitchen, switch on your hairdryer and aim it at the flies. A gentle stream of air will stop them in their tracks, putting them in prime position for swatting. The reaction of fruit flies to wind was something that had intrigued Caltech biologist David J. Anderson for some time. Read more in this news release.
Credit: Bob Paz/Caltech
The Division of Integrative Organismal Systems (IOS) of the Biological Sciences Directorate supports research aimed at an integrative understanding of organisms. The goal is to predict why organisms are structured the way they are, and function as they do.
Research from the University of Washington using high-speed digital imaging shows that, at least for some insects, wings that flex and deform are the best for staying aloft. Andrew Mountcastle, a doctoral student, used particle image velocimetry to study how air flows over the wings of Manduca sexta, or tobacco hawkmoths.
October 3, 2011
Dragonflies: The Flying Aces of the Insect World
Research focuses on aerial feats such as hunting and mating in mid-air
Next time you see a dragonfly, try to watch it catch its next meal on the go. Good luck!
"Unless we film it in high speed, we can't see whether it caught the prey, but when it gets back to its perch, if we see it chewing, we know that it was successful," says Stacey Combes, a biomechanist at Harvard University. With support from the National Science Foundation (NSF), she and her team are studying how dragonflies pull off complicated aerial feats that include hunting and mating in mid-air. She set up her lab in typical "dragonfly country."
"Our lab is at the Concord Field Station in Bedford, Mass. This is a field station of Harvard University about a half-hour from the main campus," says Combes. "We're surrounded by woods and ponds, which is an ideal habitat to find dragonflies."
The researchers have already identified 20 species at the pond so far. On this outing, they hope to net a few to study. But, it's not easy to catch a dragonfly.
"Alright, I got one ... I lost it," exclaims team member and biomechanist Jay Iwasaki. "It's a Libellula cyanea," he notes when he finally catches one. "It's in the family of Libellulidae, which are dragonflies known as skimmers; this is a male. You can tell this species in particular from the white dots on its wings."
The team takes two dragonflies back to a specially built, netted enclosure. It's large, about one and a half stories high. "We built this especially to look at predation in dragonflies. One of the problems with studying dragonflies is they tend to not go after prey if the lighting is not just right. If they're not in a large enough space where they're comfortable, they'll just starve because they only will eat this prey in midair," explains Combes.
In the enclosure, her team has set up eight high-speed cameras. They release a dragonfly along with some tasty fruit fly prey to see what happens next. The high-speed cameras catch what the human eye can't.
"They'll go up in midair, catch the prey with their feet, turn upside down and glide back to the stick, and the whole capture will take maybe a second, or a second and a half," says Combes. She points to one of the high-speed images: "This one is missing about half of its left front wing and yet, it still does an amazing job catching the fruit fly in midair."
"That particular maneuver takes only a half second to happen," adds Iwasaki.
"They're amazing fliers," explains Combes. "They're fun to watch and it's something you can't really see with your naked eyes. We look at them in high speed and look at the angles in flight as they catch prey. They flip upside down, it's just amazing and they do it time after time, hundreds of times, like it's nothing. In the enclosure they caught about 90 percent of the prey that we gave them."
Dragonflies have had a long time to evolve their skills as predators. They have been on the planet for about 300 hundred million years and predate dinosaurs. They can fly straight up, straight down, hover like helicopters and disappear in a blur.
"Dragonflies have two sets of wings and they flap in different phases," says Combes. "Sometimes they flap together; sometimes they're offset and we're seeing with our predation videos that they change this all the time."
Biomechanist Amber DesLauriers points to a dragonfly sitting on a thick blade of grass. You can see its head moving back and forth looking for its next meal. "They can pretty much see all the way around their head except right behind them," she says.
Combes says engineers are looking to the dragonfly for inspiration in small-scale aircraft design. "There's a lot of interest in building small robotic devices and when you get down to the size scale of insects, you really can't build mini airplanes. The physics don't work well to have a little, tiny airplane. You really need to have flapping or rotating wings. So, we can learn a lot from these insects," she explains.
Combes is also exploring the idea of using dragonflies for mosquito control. "They may consume 30 mosquitoes a day. They could even consume hundreds a day," she notes.
Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.
