The light emitted may vary in tint as in Prophorus in which the two thoracic organs show greenish light, and the abdominal ones show orange light. The railroad worm of America Phyxothrix emits red light at the head end and segmental rows of greenish yellow light on the abdomen. The wavelength of the light emitted is variable, in Photinus it is 520-650 mu, in Lampyrisit is 518-656 mu, and in Prophorus it is 486-720 mu. Many Asian species flash in unison. In some, at least the emission of light is a mating signal, as in Lampyris, where the wingless female attracts the flying male by her glow. In Photinus both