What is the excretory system of arachnids represented?

The excretory system of spiders is represented by a pair of thin tubes called malpighian vessels. They are a small branch of the vessels, they are blindly closed on one side in the body, and on the other side they open in the back of the intestine. The process of water absorption is formed in the intestines, thus, spiders have the opportunity to exist in arid regions. Also, in the Malpighian vessels, the product of excretion – guanine grains – accumulates. They, like uric acid, look like crystals and require a small amount of water to remove. Metabolic products can be excreted through the walls of blood vessels and through the intestines to the outside.