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Ornate Bella Moth

Utetheisa ornatrix

This moth was first described as Phalaena ornatrix and Phalaena bella by Carl Linnaeus in 1758. In 1960, it became known as the Utetheisa ornatrix by William Trowbridge Merrifield Forbes. It’s also called the ornate bella moth, ornate moth, bella moth or rattlebox moth and is in the family Erebidae.

Description The body is white with black spots on the back of the thorax and head. The legs are black and white and antennae are black and filiform. The hindwings are a pale or bright pink with an irregular black border. The forewings are orangish-yellow with white bands surrounding black dots. Patterns may vary. These colors are used to warn predators of the moth’s toxicity.

Wingspan range: 33 - 46 mm (1.3 - 1.8 in)

Diet and Habitat The larva feed on plants of the Crotalaria species such as Avon Park rattlebox, rabbitbells, smooth rattlebox, and showy rattlebox. These plants provide the larva and adults with alkaloid compounds which are the unpalatable to predators. They accumulate these toxins from the seed pods of these plants, however if the larva can’t eat a seed pod due to competition they will have to eat the leaves where is concentration is much lower. Larvae may prey on/eat others of its kind to maintain high levels of alkaloids. Alkaloids are also passed down from parents to eggs.

Its northern most range is from Connecticut westward to southeastern Nebraska and southward to southern New Mexico and Florida in the United States. Its southern most range is from Mexico, South America, and Central America. It’s southernmost reach is southeastern Brazil. This species is more common in tropical parts of this range due to host plant populations.

Mating This species demonstrates a form of sexual selection. The females choose a male to mate with based on the intensity of their pheromones. During mating, the females receive a “spermatophore” from the males containing sperm, nutrients, and alkaloid compounds. After mating, the females choose which males’ sperm fertilizes the eggs. Usually, the female chooses the male with the most alkaloids which tends to be the larger males. Adult males invest up to 11% of their body mass to create a spermatophore they provide to a female during mating. The nutrients given in the spermatophore allow the female to produce an average of 32 additional eggs in her brood.

Females mate an average of 4-5 times and up to 13 times, each with a different male. In the north there there two generations per year with more in the south.

Predators The larva and adults keep predators at bay with alkaloid compounds accumulated during feeding and inherited from parents. These toxins make them unpalatable to their main predators: spiders and bats. Specifically, the adult moth secretes an alkaloid foam from its head when threatened. However, larva and moths with low concentrations are more susceptible to predation than those with higher concentrations who are usually released and unharmed after being caught.

These toxins do not work against some predators like loggerhead shrikes.

Unlike other moths of the Arctiidae subfamily, this species moth does not have a way to audibly communicate their toxic which would help it to avoid bats altogether.

Fun Fact This species was first described on 1758 by Carl Linnaeus as two different species: Phalaena ornatrix was used to describe the paler moth specimens, and Phalanea bella, described the bright pink moth specimens. It was then moved to the genus Utetheisa in 1819 by Hübner. After nearly a century of struggling to identify this species and its subspecies, Forbes combined both species Utetheisa ornatrix and Utetheisa bella into one in 1960: Utetheisa ornatrix.

(Source: Wikipedia; The Island Packet; Institution of Food and Agricultural Sciences, University of Florida)