 Well, our next topic is the excretory system in insects. So, what are insects? These are the arthropods which have six legs. There are three pairs of legs. We call them as the insects or six-legged animals. So, the excretory system is associated with the digestive system. The excretory system is not different at all. It is associated with a tubular system. So, insects have excretory system made up of gut and malpigean tubules. These excretory system tubules are called malpigean tubules which are attached to the gut. That means that digestive system and excretory systems are not different. They are connected to each other. Excretory excretion involves the active transport of potassium ions into tubules from the surrounding hemolymph and the osmotic movement of water that follows. Well, in this diagram, we can see that the digestive system or excretory system is associated with each other in this group of animals. So, this mouth leads into the esophagus, then there's a chamber which is the crop, then there's the stomach, and between these two, there are gastric glands. These are gastric glands. And then there's the stomach which we can call as the mid-gut, and then there's the intestine which is broadly speaking to the hindgut. And between these two, where you get them, there are a lot of malpigean tubules. And these malpigean tubules are very fine and numerous which are floating in the hemolymph. And in this liquid, where there's water, and there's surplus water, night with the waste, which is colorless blood in fact, and it absorbs from here. And then there's the intestine, and the rectum after the intestine, and then this is the anus. So, in this, we can see that the malpigean tubules which are excretory system in fact, are connected with the digestive system. So, nitrogen waste and these animals because they have very little water supply. Like this grasshopper example. So, they only eat grass, and the water that goes with them is the same water which is their intake in the intestine. So, the water supply is very, very less. And then when these proteins metabolize, then ammonia, ammonia is made by urea and then euric acid. Euric acid because relatively less toxic so, these animals prefer to synthesize this euric acid as compared to ammonia. So, here we can see that this tube which is the digestive system, and this is the malpigean tubule. So, this is diagrammatically and it is shown by enlarging it. What's outside? This is all hemolymph. This is all hemolymph. And this is midgut, and then this is rectum, and then this is the anus. And this is malpigean tubule. What's inside the malpigean tubule? And it is from the outside which is a hemolymph which is water, sugar, and amino acids they move, they are reabsorbed. Reabsorption is there. And sodium or potassium B that is being absorbed, it is moving into the malpigean tubule and the euric acid is going from this hemolymph. And as the fluid moves through the malpigean tubules some of the water and certain ions they are recovered. They move back into the body, into the intestine. So, all the euric acid passes into the gut and out of the body. But euric acid because it is a nitrogen waste this is not reabsorption for it but it is from the malpigean tubule it enters in the gut and then it comes out of the body in crystalline form. Now the malpigean tubules remove nitrogen waste which is mostly euric acid from the hemolymph which is a liquid part. Now various ions are actively transported across the outer membrane of the tubule. This is the active transport. You get this from lower to high concentration movement. Now water molecules, water flows water follows these ions into the tubule and carries amino acid, sugar and some nitrogen waste along passively. This is their passive movement from high concentration to low concentration. So this is a passive transport or active transport this is always movement from low to high concentration. Now some water, some water, ions and organic compounds they are reabsorbed in the basal portion of the malpigean tubules and the midcut. The other portion is the proximal portion of the malpigean tubules. So there is the reabsorption of the organic compounds there is the reabsorption of the organic compounds and the fecal matter and then it moves down it moves back into the after passing through the intestine into the rectum because there is nitrogen waste so fecal matter and nitrogen waste this external opening which is called as anal opening that is then removed from the body. So this is all about the excreted system of insects.