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 That'true. monarch butterflies lay their eggs on milkweed plants.The caterpillars feed on milkweed, from which they extract substances called cardenolides, a type of chemical that can cause heart arrhythmia. This toxin doesn’t affect the caterpillars themselves, but it makes them poisonous or distasteful to most predators.But it’s not just monarchs that like milkweed, scientists are discovering new uses for many parts of this perennial plant that grows along roadsides and fields. The large seed pods contain thousands of seeds, each with a feather white tuft of silky fibers. These fibers help the seeds disperse in the wind.It turns out that these milkweed fibers are excellent insulation, superior even to down feathers. One company has started marketing milkweed fiber as hypoallergenic filler for comforters and pillows.Chemists at the National Center for Agricultural Utilization Research have also discovered that the seed pulp left after the fibers are removed can be used to kill destructive soil nematodes and other agricultural pests.Yet another study found that milkweed oil is high in vitamin E, and is free from the toxins found in other parts of the plant. The oil from milkweed can make an ideal ingredient for moisturizers, cosmetics or even biodiesel fuel.