Urania ripheus – the Sunset Moth
20x15x6cm handmade red frame
Underside display; no antennae
One of the most stunning specimens available. The bold and iridescent colours come from optical interference rather than pigmentation, so the colours appear different depending on the angle from which it is viewed. The colours serve to warn predators that it is toxic if eaten.
Urania riphaeus (also known as Chrysiridia rhipheus, or the Madagascan sunset moth) is not a butterfly but a day-flying moth, although when it was first described it was placed in the swallowtail family – this error was due to the original specimen having had its head substituted for a butterfly’s, with clubbed antennae, rather than keeping its own with the unmistakable brushy antennae. (Unfortunately some of these specimens arrived with broken antennae - which seems to be a common theme with these moths – so I have removed the remnants.)
It is endemic to Madagascar, where it has an interesting relationship with its host plant:
The moths migrate in response to changes in the host plants. Chrysiridia larvae defoliate the whole plant, and even eat the flowers and fruit, and thus have a considerable negative impact on the reproduction and survival of seedlings. The plants probably react by changing their nutrient and secondary compound levels, becoming toxic to the larvae and causing high mortality. Omphalea populations that are not damaged by moths for long periods of time have lower toxicity. These factors cause mass increases in local population, followed by sudden crashes. The population crashes might result from increased larval mortality, but are more likely caused by the emigration of the adult moths. Through semiochemicals, the plant may recruit hymenopteran parasitoids as a protection, hence playing a role in the population dynamics of the moth.