More recently, behavioral experiments have investigated the functions of visual perception in "Limulus". He concentrated his studies on the eye of the horseshoe crab ("Limulus polyphemus"). Approximately 500,000 "Limulus" are harvested annually for this purpose. This enzyme is present in the hemocyte granules of horseshoe crabs Limulus and Tachypleus. He further suggested a kinship with "Limulus", the modern horseshoe crab. Therefore, the preservation of limulus is to protect species diversity. Both of them gave evidence that limulus sauce has been for a long history. Limulus sauce also has special medical function for digestion. Currently, one common method for endotoxin detection is the Limulus Amebocyte Lysate (LAL) test. The most studied cartilage in arthropods is the "Limulus polyphemus" branchial cartilage. The Hao Kuih also keep the shape of limulus only without the limulus sauce. In "Limulus", there are no metatarsi or pretarsi, leaving six segments per leg. Since people stop killing limulus, they use some sea food like shrimp to replace it. Traditionally, people use local potato flour, rice and limulus sauce to make Hao Kuih. After knowing its fatal poison and its decreasing number, people begin to stop killing limulus.