How do ants crawl on walls? – Ethan, 9, Dallas, TX
When I started my job as a biologist at the University of South Florida, I drove my Jeep into a grassy field, dug up a mound of fire ants, and shoveled it into a 5 gallon bucket. Immediately, thousands of ants sprung up from the ground and climbed up the sides of the bucket towards freedom. Luckily I had a cover.
How do ants make climbing walls, ceilings and other surfaces so easy? I have been studying ants for 30 yearsand their climbing abilities never cease to amaze me.
Human hands vs ant feet
To understand the feet of ants, it is helpful to compare them with human hands. Your hand has a large segment, the palm. Four fingers and an opposable thumb protrude from your palm. Each finger has three segments, while your thumb has only two segments. A hard nail grows from the fingertips and thumb.
Humans have two hands – ants have six feet. Ant Feet are similar to your hands but are more complex, with an additional set of odd-looking parts that enhance them.
Ants’ feet have five jointed segments, with the terminal segment bearing a pair of claws. The claws are shaped like a cat and can grab the irregularities of the walls. Each foot segment also has thick and fine spines and hairs that provide extra traction by sticking in microscopic pits on textured surfaces like bark. Claws and thorns have the added benefit of protecting ants’ feet from hot pavement and sharp objects, much like your feet are protected by shoes.
But the feature that really separates human hands from ant feet are the inflatable sticky pads, called arolia.
Arolia are located between the claws at the end of each ant foot. These balloon-shaped pads allow ants to defy gravity and crawl across ceilings or super-hard surfaces like glass.
When an ant walks on a wall or ceiling, gravity causes its claws to spread and withdraw. At the same time, the muscles in his legs pump fluids into the pads at the end of his feet, causing them to swell. This body fluid is called hemolymphwhich is a sticky liquid similar to your blood that circulates throughout an ant’s body.
Once the hemolymph has swelled the cushion, some leaks outside the cushion, which is how ants can stick to a wall or ceiling. But when an ant takes its leg, its leg muscles contract and suck most of the liquid into the pad, then move the leg up. This way, an ant’s blood is reused over and over again – pumped from the leg into the pad, then sucked back into the leg – so that none is left.
Ants are light as a feather, so six sticky pads are enough to hold them against the force of gravity on any surface. In fact, at home in their underground chambers, ants use their sticky pads to sleep on the ceiling. By sleeping on the ceiling, the ants avoid the peak hour traffic of other ants on the bedroom floors.
A unique approach
When you walk, your left and right feet alternate so that one is on the ground while the other is in the air, moving forward. The ants also alternate their feet, with three on the surface and three in the air at a time.
The walking pattern of ants is unique among six-legged insects. In ants, the left front and rear feet are on the ground with the right middle foot, while the right front and rear feet and the left middle foot are in the air. Then they change. It’s fun to try copying this triangular pattern using three fingers on each hand.
The next time you see an ant crawling up a wall, look closely and you might witness some of these fascinating features at work.
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