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Binomial name: Urania fulgens (Walker, 1854)
Common name: Urania swallowtail moth
Geographical range: United States, Mexico, Costa Rica, Bolivia, Panama, Ecuador,
Host plants: Caterpillars exclusively feed on Omphalea (Euphorbiaceae). Omphalea diandra, Omphalea oleifera and will potentially accept more plants but only within the genus Omphalea
Habitat: It is hard to generalise the habitat of Urania fulgens, since the adult migrates throughout Central and South America over extremely large distances. The adults have even been recorded in North America (Texas, Florida) as vagrants but they are more often found in Central America (Mexico, Panama, Costa Rica and more) and South America (Colombia, Ecuador). The adults seem to require warm to (mostly) tropical environments but can survive in a broad spectrum of habitats. Despite this information however, they only reproduce in environments where Omphalea plants are present. The food plants of Urania fulgens are found in wet or moderately wet woodlands on limestone, mostly in lowland habitats but also occasionally found at higher elevations on shale. While the distribution of Urania fulgens is very large, there are gaps in their reproducive range since they are restricted to habitats with suitable Omphalea food plants.
Flight time: Always. Adults of this continuously brooded species can be seen all year. However, due to its nomadic lifestyle it can ubiquitous in certain regions only to suddenly dissapear from the region for months or years.
Ecology: Diurnal (day active) moth species, often confused with a butterfly. Urania fulgens is highly nomadic and famous for its mass-migrations consisting of millions of individuals. Interestingly, while it has a fairly large distribution, there are reproductive gaps throughout the range of this species, and it would be reasonable assume that individuals of Urania fulgens migrate between their reproduce habitats for various reasons, such as the constantly changing suitability of these habitats. “The moth has reproductive populations in Veracruz, Mexico, south on the Pacific side to Guatemala and El Salvador then there is a gap in distribution. Reproductive populations have again been reported from Costa Rica and Panama (Smith, 1992)”. Urania fulgens exclusively lay eggs on Omphalea sp. plants and caterpillars exclusively eat Omphalea, although they seem to utilise several plant species from this group such as Omphalea diandra, Omphalea oleifera and other species if given the chance. Urania moths and Omphalea plants have co-evolved and the constant arms race between herbivore and host-plant may be one of the explanations for their migratory lifestyle. The following report I found in the report also solves a piece of the puzzle:From Smith, Neal G. 1983. Host plant toxicity and migration in the dayflying moth Urania. Florida Entomologist 66(1):76-85. In this report it is concluded that Urania species simply need to migrate. This is because their food plants are slow growing, tropical vines in the genus Omphalea. Interestingly, when the caterpillars of Urania feed on these food plants, the host plants slowly start to release more toxins. These toxins lower the survival rates of the caterpillars and allow the plants to “fight back” against their main herbivore enemy, Urania moths. Over the course of several years, food plants in habitats in Urania moths will become unsuitable for larval consumption. This explains why day-flying Urania moths can be over-abundant in some areas for months or years and then suddenly seem to vanish. They are forced to live a continuously nomadic lifestyle, dissapearing from and revisiting habitats made unsuitable or suitable due to larval infestations. It is thought that host plant toxicity and migration cycles are interconnected. In fact, there is evidence that a high concentration of toxins in the food plant leaves consumed by caterpillars results in migratory adults, while a low concentration of toxins results in “residental” non-migrating adults. The population dynamics and fluctuations of day flying Uraniidae moths are heavily regulated by the capabilities of their food plants to “fight back” and produce toxins in response to larval grazing; nomadic adults simply seek out ungrazed, and thus less toxic plants. The moths are also slightly toxic to predators since they sequester toxins from their host plants – the evolutionary relationship between Urania sp. and Omphalea is beneficial for the moth, since the toxins in the Omphalea make sure there is little competition over their food plants, but they also provide the larvae and adults protection by making them unpalatable by storing said toxins in their fat tissue (sequestration). Urania fulgens are diurnal moths that feed on flower nectar, and adults can sometimes be seen flocking over their favorite nectar plants such as avocado flower (and many others) in high numbers.
Description adult: Somewhat resembles a Papilionidae butterfly in appearance; wings predominantly black with green metallic bands.
Description larvae: Black caterpillars decorated with tiny white stripes and an orange/red head capsule. The caterpillars have noticable ‘flagellae’ (broad, almost “feather”-like) hairs that protrude from the thoracical segments.
Diapausal state: No diapause known
Similar species: Mainly other Urania species in the region, but the species can be separated by geographical range. Such as Urania boisduvalii (Cuba endemic), Urania poeyi (Cuba endemic; restricted to eastern Cuba), Urania brasiliensis (Brazil, Atlantic rainforest), Urania sloanus (extinct species – used to be endemic to Jamaica), and Urania leilus (South America – Suriname, French Guiana, east Colombia, Venezuela, east Ecuador, Brazil, north Bolivia, east Peru, and Trinidad). The geographical range of Urania fulgens never or rarely overlaps with other species and the moths can be distinguished by their geographical origins. The only country where both Urania leilus and fulgens are found is Ecuador, but these populations are seperated by the Andes – fulgens is found on the western side of the Andes, while Urania leilus is found east of the Andes. Although many Urania sp. are similar looking they can also be identified by appearance.
Dimorphism: The differences between males and females are there, but hardly noticable unless you can directly compare individuals. Males are slightly smaller with more slender wings while females are slightly bigger with broader wings. If in doubt, the genitalia should be inspected.
Health information: Considered harmless
Fun fact: Because of its migratory nature, this species can be found in abundance in various localities only to completely dissapear for multiple years. The population dynamics of Urania fulgens are poorly understood, but it is famous for the massive migrations that have been observed, consisting of millions of individuals passing through certain regions in a short time.
Other media: Video available (Click here)
Photography: All specimens photographed here were part of a captive breeding experiment in the Netherlands (Europe) and are live specimens. Although captive livestock does not look very different from wild animals, they are not wholly representative of wild animals since captive livestock is prone to exhibiting unnatural variations and sizes. I am a moth breeder from the Netherlands that has bred hundreds of species. This website only features the imagoes of Lepidoptera I photographed and not the early life stages.
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