butterflies on a flower

butterflies on a flower

Butterflies are not the best flyers. Instead of producing more straight flight pathways, their vast wings lead them to flap around.

Butterflies are not the best flyers. Instead of producing more straight flight pathways, their vast wings lead them to flap around. However, their fluttery flying makes it difficult for predators to grab them. Recent research explains why. During takeoff, butterflies flap their wings over their bodies. The maneuver generates jet thrust for a speedy escape. 

Butterflies Are Winging It

Christoffer Johansson and Per Henningsson are evolutionary ecologists at Lund University in Sweden who research the development of animal flight. A previous study showed that the above wing clap of a butterfly propels the creature forward. The wing clap, according to researchers, presumably produced a pocket of air that bursts out like a jet. But no one has put that to the test. 

Johansson and Henningsson captured six butterflies in a meadow near their lab. These silver-washed fritillaries were kept in net enclosures and given honey water. The scientists placed the butterflies inside a wind tunnel one at a time to study their flying. 

Fans are used in wind tunnels to circulate air at particular speeds. When an item is placed in the tunnel, air must circulate it. This allows researchers to investigate how things travel through the air. “Smoke” consisting of tiny innocuous droplets of oil is frequently introduced so that researchers may accurately examine how air moves around something. This demonstrates how aerodynamic the item is.

Fans circulated the air just enough to maintain the smoke uniformly dispersed throughout the tunnel for this research. A laser was also utilized to illuminate a layer of smoke in the tube directly behind the butterfly. Four high-speed cameras set around the feeding station caught the butterfly’s movement and the smoke as it took flight. The researchers positioned a butterfly at a feeding station in the middle of the tunnel for each trial. When the butterfly went off on its own, they began filming. 

Forming a Vortex

They examined 25 takeoffs by the six insects. After takeoff, each contained up to three wingbeats. The butterflies flapped their wings together more frequently during the initial few wingbeats than later in the flight. 

A vortex is formed when air or water, similar to a whirlpool, swirls around a central point. The pictures of the butterfly pathways showed air whirling in a vortex as the butterflies flapped their wings. The images also indicated that the downstroke of the wings pushed air down. This generated a force that propelled the butterfly upward. When the wings raised to clap, they created an air pocket. This pocket generated a powerful jet of air that blasted out between the butterfly’s wings behind it. The bug was pushed forward by the jet. 

The wings’ combined forces produce a fluttery flying pattern. As their wings move down, the butterflies ascend, and as their wings move up, they fly forward. The butterflies flew away swiftly thanks to a wing clap on takeoff and a rapid spin. “The butterflies must be able to take flight quickly to reduce the chance of being caught” by predators, says Henningsson.