We have some fearful species living in this world with us and spiders are common contenders in that category. This is why ‘Why do spiders curl up when they die?’ is a question not commonly asked. People, mostly in urban areas, when coming face to face with a spider, can only think about how to get rid of it. Nothing past that.
It seems justified too frankly because people in the majority are not aware of spider anatomy that could help them recognize the harmful from the harmless. When there is no basis for differentiation, every spider is a suspect killer. Also, they creep people out. They are the poster species for the term ‘creepy crawlers’. Other crawlers walk behind spiders, following their path, always being secondary in the terror-spreading list. The only thing that might have helped the spiders a little bit with their image is the Spiderman comics and movie franchise.
Regardless of the fear, there is some confusion regarding the state in which the spiders die. For the curious folks who want to know why they curl upside down, with legs in the air, this article will answer your questions.
Have you ever killed a spider? If yes, then you probably saw it up close later when trying to get rid of it. After they die, they curl up and their legs hang in the air. It is a strange sight when you consider it, why go through all the trouble? They could just give outstanding on their legs and it would not be as strange. Well, there is entire anatomy to consider here that makes spiders end up this way.
Usually, in the anatomy of legs, there are flexor muscles and extensor muscles. These muscles help contract the legs and extend them whenever required, respectively. However, it turns out, spider anatomy is not so balanced in the muscles category. The eight-legged crawlers do not have any extensor muscles to help their legs stretch out as they please. Instead what they depend on is their blood pressure.
If that seems incredulous, do not worry, you are not the first one to be astonished. Imagining the blood pressure of your body being the only thing that keeps your limbs moving seems very dependent. But it is true for spiders nonetheless, they rely on their blood pressure spike to stretch and extend their limbs while they move around.
How it works out is still very much simple, our bodies are made to function as a group. Whenever they need to extend their legs, blood is pumped into their legs to stretch them out. Using the pressure from the blood their heart pumps out, they maintain the mobility of their legs. The entire process means their flexor muscles work with the blood pressure pumping through their body to do the daily tasks of walking, moving around, and others.
This process is continued for spiders to perform any task that requires their legs to be mobile. If you have already connected the dots then you have your answer. When spiders die their heart stops working. Simultaneously blood stops pumping out, and the pressure that keeps the legs moving by helping them extend out and stretch halts too. Only the flexor muscles that work according to their job description bring the legs back to their original position contracting them inwards.
It is easy to imagine how they resort to flipping over on their back when they die because of how their legs work internally. Many people also ask the question of why spiders are never seen bleeding even when they are injured, miss a leg, etc? That is because their body is not made of vessels like humans.
Rather, spiders have an open circulatory system which means their blood flows openly in their entire body. And they have a very prompt response system in their body that seals off any missing leg and injury immediately to prevent major blood loss. This is why they do not immediately die when they are injured or their leg is cut off.
This was the reason why spiders curl up when they die, because of the hydraulic system created by their bodies through the use of their blood pressure. Nature is truly fascinating in both how it exists around us and how it keeps our bodies together internally, whether it’s for us humans or some creepy crawlers.