spider consulting
Question: Do spiders urinate? (why I get this question so often, I don't know)
Answer:spiders have structures designed to get rid of nitrogenous waste. These are called malpighian tubules and function in a manner similar to our own kidneys. Spiders don't produce urine like we do, but produce uric acid, which doesn't dissolve in water and is a near-solid. Spiders have this alternate form of waste because they can't afford to lose as much water as we do. These malpighian tubules drain into an pouch attached to the digestive tract (called a stercoral pocket) so the uric acid waste from the "kidneys" is combined and eliminated together with solid waste from the digestive tract. In this sense, spiders don't deposit separate feces and urine, but rather a combined waste product that exits from the same opening (anus).