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Milkweed Tussock Moth Caterpillars are poisonous, as evidenced by nature's characteristic warning colors. They become poisonous by eating milkweed leaves which contain a cardiac poison. So, nothing eats them. But the adult Tussock Moth is comparatively drab brown, and would be prey only to bats. It also is poisonous, but at night-time and without bright coloration, the adult moth has evolved an organ that warns away bats with an ultrasonic signal easily detected by bats. The signal warns the bats to avoid a noxious distasteful mouthful.