Milkweeds are flowering plants in the dogbane family (Apocynaceae), in the subfamily Asclepiadoideae. They are named for their milky sap, which usually contains toxic chemicals such as alkaloids and glycosides. Most insects will not feed on them, but the caterpillars of monarchs and other members of the milkweed butterfly family feed primarily on milkweeds. They sequester the toxins, making the caterpillars and adult butterflies toxic to predators such as birds. Nationwide decline in monarchs seems to be due to high use of agricultural pesticides, as well as habitat loss. Protection of native prairies where milkweed is found helps to reduce declines in monarch butterflies. The Weston Ranch has 8 species of milkweeds, as shown below.