Gaining Traction

Winter in the Midwest includes below freezing temperature and slipping on ice. Why is ice slippery? Loss of friction! When we put pressure on ice with our foot, the thin layer on top melts due to the increase in pressure. The thin layer of water can move freely and lowers the friction between our feet and the ground. The water has a much lower coefficient of friction than does dry land, thus our feet fail to get sufficient traction on ice. We are gliding on a thin film of water.

Friction increases with weight. Large animals, such as humans, can generate plenty of friction on dry ground. Very large animals, such as elephants, have enough weight to generate a lot of friction on a relatively flat foot. Feet (elephants have much larger feet than humans) are a small enough size to create sufficient friction for walking, yet large enough to keep the animal from sinking too far into the ground.

Like a person walking on ice, an insect with flat feet would have trouble getting traction on dry land because of their small size and weight. To gain traction, insects make use of an array of claws and spines or in some cases sticky hairs.

The end segment of an insect leg, the tarsus, often contains a claw. The claw can dig into the ground or into the stems or leaves of plant, much the way that cleats on shoes will provide additional traction for human athletes. The ability to dig into the ground is a function of the pressure applied. The pressure generated is the weight divided by the surface area. Insects have little weight to generate friction or pressure. Instead, insects maximize the pressure (weight per unit area) by reducing the area. By putting all of its weight on the small surface area at the end of a claw, insects can gain the traction they need without slipping and sliding through life.

Tarsal Claws Give Small Insects Traction

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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14 Responses to Gaining Traction

  1. Nathan Queisser says:

    The very first paragraph of this article caught my attention because I never really knew why ice was so slippery besides the fact that it has less friction. I didn’t know that some of the ice melted when stepped and created a thin layer of water between the persons shoe and the ice. I also never really knew how insects could climb things so easily. I think that the concept of the tarsus is a very good mechanism for the insects to climb. Since the tarsus reduces the insect’s surface area to a single point, it allows the insect to easily climb whatever it wants to.

  2. Justin Amber says:

    This article was very interesting because I not only learned about how insects are able to walk on icy surfaces but humans and other large animals as well. It was especially interesting to me to learn that there is a small layer of ice that actually melts when contact is met with the touch of a foot, appendage, or whatever a living creature uses to walk on icy surfaces. Another thing that intrigued me was the claws and sticky hairs that insects use to walk on slippery surfaces, it is truly incredible about the world around humans which can’t be seen with the naked eye. Lastly, I feel this article has will help me with taking more observations of my cockroach over the semester (how it climbs, grabs items, etc.)

  3. Chris Clarkson says:

    “Learned something new”

    I know a lot about friction from previous classes such as physics and I live around a lake so I know a lot about what this article started out talking about. I wondered were is was going when I started reading it. I find it very interesting how insects deal with there tiny size. Insects and humans are so different in the way that they have to approach life. Being so small must be a difficult task in a land filled with giants in comparison. The insect is one of the most well adapted animal in my opinion.

  4. This article caught my attention because who could think that some hairs on some claws would allow insects to not slip or keep good traction when we have hard enough problem doing so. Insects can make it look easy and they are not even close to the same size. The fact about a film of water developing between our feet and ice we walk on was also interesting even though that is basically what i thought happened when we did run on ice.

  5. Elliott Stewart says:

    I enjoyed reading about not only how insects gained traction but also how human loss traction. I never really understood how a bug can climb vertical things so easily. I find it interesting that even though bugs have very little pressure to push down with they make the most of their weight by making their surface area so small.

  6. Sean Conrad says:

    This article caught my attention because it started out talking about ice and loss of traction. That is mainly because of all the ice and snow we’ve been getting around campus in the past couple of days. Also I do enjoy the clear explanations about how animals big and small gain traction. Finally it is interesting to finally know exactly how insects can get around so easily such as climbing trees.

  7. Chase Sullivan says:

    It is amazing to me how different living thing have much different ways of doing things. It is very interesting when comparing elephants and insects. Everything is so much different. Two feet of snow wouldn’t stop a human or an elephant, but definitely would stop an insect on the spot. I find it very interesting to learn how they have techniques to gain traction on slick surfaces. They actually have an advantage in certain areas. They can scale walls and crawl on ceilings. That would be amazing if humans could do that.

  8. Tiffany Teeguarden says:

    “New Things Learned about Gaining Friction”

    I found this particular post to be very interesting because it has been snowing a lot recently and it also gives the reader a copious amount of information. I previously did not know that ice melts when a foot presses down on the ice, therefore making the surface slippery. I also found it interesting how different animals such as elephants were used in order to demonstrate how they react when they encounter ice. I also found it impressive how insects have a claw on the end segment of their legs which allows them to successfully maneveur around on slippery surfaces. Overall, this post was both informative and interesting.

  9. Ross Peare says:

    “Human Spiderman?”

    It is extremely hard to believe how similar insects and humans can travel under different environmental conditions. Size is the only factor that separates us from transportation. The claw is the only innovation insects have over humans, which allows them to scale trees and branches, as well as, travel across icy conditions. If they did not have the claw, they would most likely blow away in the winter breezes during a snowstorm. Friction truly is a beautiful thing when it comes to walking on land, and most animals, along with insects, take this for granted. If only we, as humans, had claws we could travel up trees, and everyone could be a “spiderman.”

  10. Abigail Fassnacht says:

    This post caught my attention because we have been learning about the locomotion of insects recently in class. The post is also relevant to us, because of the recent snow/ice storm. I find it interesting that insects have so many modifications to them to help walk, especially sticky hairs and a claw. It made me think about what kind of modifications humans have, which would be something like our toes to help us balance. It is interesting how this is isn’t a known fact to most people because it’s hard to see something like that on an insect because they’re so small. Insects have a much different way of getting around an obstacle like a snow storm than humans do.

  11. Taylor says:

    I was interested in this post because I didn’t think about how insects need traction to move around especially when there’s ice and slippery conditions. It came to my attention because of the storm that just recently hit us. I know there are some insects who need to move around in winter and I was not aware of the way they use their bodies to be mobile. When I read about how their “claws” and “sticky hairs” are used to walk, I realized that I never would have known that because it is not easily seen by the naked eye. I was also not aware that ice melts when one steps and creates a thin layer of water, therefore creating a slippery feeling. This post makes me think about what we humans could be capable of if we used our feet the way insects do. If only we knew.

  12. Spencer Graybill says:

    I first became interested in this post when I saw the picture of the claw at the bottom. I remembered listening in class about how insects use their claws to hold on to the stems of plants. I think it is very interesting how some insects have sticky hairs that can hold themselves onto vertical surfaces. The cockroach I have for the take home project can scale the vertical walls of its shoe box container. I also think it is interesting how differenct insects use different means to gain traction as they travel through life.

  13. Gregory McCotter says:

    “Little Claws”

    Very interesting read! I never understood why some insects had those small claws and how they were able to maneuver easily at odd angles on plants and such. It’s also good to know why I have been slipping all over Purdue this winter, I was just under the assumption ice was naturally slippery, but it’s pretty cool to know the actual science behind it!

  14. Jarod Satterfield says:

    The article gave really good information on friction in general and how bugs can overcome friction problems. I didn’t actually know that ice turns water when we step on it although when brought to attention it makes perfect sense. I wonder if humans had features like these if we would be able to benefit from them(maybe even climb walls??). The post was very informative.

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