Locoweeds belong to the large and diverse genus of flowering plants Astragalus (Fabaceae), with approximately 2,000 different species in the northern hemisphere, 380 species in North America, and 94 species in California. Some are rare endemics that only occur in one isolated mountain range or canyon. They are sometimes called milkvetches from the notion that milk secretion in goats was increased when they fed on the common Old World forage species (Astragalus cicer). Like many legumes, the leaves are typically divided into a dozen or more leaflets, and the flowers resemble small pea blossoms. Some species produce inflated seed pods that make a distinct popping sound if you step on them. Locoweeds are also called rattleweed because of the bladder-like, inflated pods, particularly when a gust of wind rattles the seeds inside. Astragalus is derived from a Greek word meaning anklebone, the plural of which means dice. Perhaps the dice connotation refers to the rattling of seeds inside papery pods, like the sound of dice in a thrower. In anatomy, the astragalus or talus is one of seven bones in the ankle joint. Anklebones were apparently used for dice by ancient Greeks, and to this day, veteran crapshooters in Las Vegas refer to dice as "bones." Since adult astragalus bones are a little too large for dice, some of the smaller, cuboidal or cuneiform anklebones were probably used.