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common name: ornate bella moth, rattlebox moth
scientific name: Utetheisa ornatrix (Linnaeus) (Insecta: Lepidoptera: Erebidae: Arctiinae)

Introduction - Synonymy - Distribution - Description - Life Cycle and Biology - Hosts - Natural Enemies - Selected References

Introduction (Back to Top)

The ornate bella moth, Utetheisa ornatrix (Linnaeus), is one of our most beautiful moths (Figure 1). Unlike most moths, which are nocturnal, the ornate bella moth is diurnal and flies readily when disturbed. Therefore, it is more commonly seen than nocturnal species of moths by the public.

Adult and larva

Figure 1. Adult and larva of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Lary Reeves, Entomology and Nematology Department, University of Florida.

Synonymy (Back to Top)

The adult ornate bella moth is highly variable in coloration which has resulted in confusion regarding its taxonomy and the assignment of many names to the numerous color "forms". Linnaeus (Linnei 1758) originally described two species in the genus Phalaenaornatrix (more whitish or pale specimens) and bella (brightly colored specimens), and Hübner later moved them to the genus Utetheisa. Forbes (1960) included both forms under the species Utetheisa ornatrix.

Distribution (Back to Top)

The ornate bella moth is found from Connecticut westward to southeastern Nebraska, and southward to New Mexico, southeastern Arizona and Florida (Covell 2005, Powell & Opler 2009, North American Moth Photographers Group Undated). It is also found through Mexico and southward through Central (Powell & Opler 2009) and South America all the way to Argentina (Pease 1968) and throughout most of the Antilles (North American Moth Photographers Group Undated). In the U.S., it is more common in the southern part of its range.

Description (Back to Top)

Eggs: The eggs are white to yellow and spherical (Figure 2).

Eggs of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 2.  Eggs of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Larvae: The larvae are orange-brown with broad irregular black bands on each segment (Figure 3). Full-grown larvae are 30-35 mm in length. There are distinct white spots on the anterior and posterior margins of the black bands. Whereas most arctiine larvae have verrucae (elevated wart-like areas on the cuticle) bearing many setae, Utetheisa larvae lack verrucae, and setae occur singly (Habeck 1987).

Larva of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 3. Larva of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Pupae: The pupae are black with irregular orange-brown bands and are covered with a loose layer of silk (Figure 4).

Pupa of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 4. Pupa of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Adults: The adult ornate bella moth is a rather small moth (wingspan 3.0 - 4.5 cm). The more common "bella" form has the front wings yellow with white bands each containing a row of black dots, and the hindwings bright pink with an irregular marginal black band (Figures 5 and 6). The paler form originally designated "ornatrix" is restricted to southern Florida and southern Texas.

Adult bella moth, Utetheisa ornatrix (Linnaeus), on fruit of lanceleaf rattlebox, Crotalaria lanceolata E. Mey.

Figure 5. Adult ornate bella moth, Utetheisa ornatrix (Linnaeus), on fruit of lanceleaf rattlebox, Crotalaria lanceolata E. Mey. Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Adult bella moth, Utetheisa ornatrix (Linnaeus). with wings spread.

Figure 6. Adult ornate bella moth, Utetheisa ornatrix (Linnaeus). with wings spread. Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Life Cycle and Biology (Back to Top)

The ornate bella moth has two generations northward but may breed continuously in the southernmost parts of its range (Covell 2005). Eggs are laid in clusters on the foliage. Upon hatching, the young larvae feed on the foliage. In laboratory studies, young larvae fed on foliage of native species of Crotalaria developed faster than those fed on foliage of exotic species (Sourakov 2015). After feeding briefly on foliage, the larvae move to the unripe pods which they bore into to feed on the seeds Upon reaching maturity, larvae migrate from the host plant to pupate in sheltered situations under loose bark on nearby trees, in thick vegetation, or in debris.

Much of what we know about the biology of the ornate bella moth is due to the fascinating work of Thomas Eisner and his colleagues and graduate students. This work is summarized in his book, For Love of Insects (Eisner 2003, Chapter 10). The biology of the ornate bella moth is intricately intertwined with its Crotalaria host plants. Crotalaria plants (particularly the immature seeds) are laced with pyrrolizidine alkaloids. Immature seeds contain approximately five times the amount of pyrrolizidine alkaloid as the foliage (Ferro et al. 2006). Ornate bella moth larvae sequester these chemicals and become poisonous (and usually repellent) to predators. The alkaloids are retained in the pupal and adult stages and are ultimately passed on to the eggs.

Adults are concentrated in patches of Crotalaria. Males become active approximately 1-1½ hours after sunset and are attracted to females by a pulsed (Connor et al. 1980) sex attractant pheromone - composed primarily of the 21 carbon triene (3 double bonds) chemical Z,Z,Z-3,6,9-heneicosatriene originating from glands at the tip of the female's abdomen. The pheromone also contains diene and tetraene forms (two and four double bonds, respectively) (Connor et al. 1980, Jain et al. 1983). (For chemical structures of Utetheisa ornatrix pheromones, see El-Sayed (2014).

Males convert some of their Crotalaria alkaloids to a related compound hydroxydanaidal (HD), and upon approaching a female, expose two eversible brushes (coremata) from the tip of the abdomen that contain HD saturated scales (Conner et al. 1981, Connor et al. 1990). Fanning the female with the coremata stimulates her to raise her wings exposing her abdomen. The male then lands beside her and copulates. In addition to sperm, males also transfer nutrients and HD to the female during mating via the spermatophore. The concentration of HD in the coremata is correlated with the amount of alkaloid carried by the males. Females measure the HD concentration of males and use that information for selecting males with the potential to donate the most pyrrolizidine alkaloids in the spermatophore (Conner et al. 1981, Dussourd et al. 1991, Iyengar et al. 2001). Higher HD alkaloid levels in males is correlated with larger body size which is a heritable trait (Iyengar & Eisner 1999a&b). Therefore, by selecting males with higher gifts of HD alkaloid, females are simultaneously selecting for increased male body size – a trait that will be passed on to her progeny. Furthermore, females are able to control which sperm fertilize the eggs, and those from larger males are more likely to fertilize the eggs (Egan et al. 2016, LaMunyon & Eisner 1993). The mechanism by which females control the flow of sperm is unknown, but LaMunyon & Eisner (1993) hypothesized that females make the decision based on the degree of distension of the bursa copulatrix (insect vagina) by each spermatophore. The larger spermatophores of larger males would cause greater distension of the bursa.

Adult ornate bella moths live approximately three weeks and females mate on average four to five times and as many as 13 times — each time receiving additional nutrients and alkaloids as nuptial gifts via the spermatophores. The additional nutrients allow the female to lay a larger number of eggs than would otherwise be possible. During oviposition, the female contributes not only her own alkaloids, but also those received from the male to her eggs making the eggs even more toxic to potential predators. Bezzerides and Eisner (2002) have demonstrated that individual eggs from multiply-mated females receive alkaloids from more than one male. The female herself also gains additional protection from predators due to the additional alkaloids from the male spermatophores (González et al. 1999).

Because most of our common Crotalarias are introduced weedy species and toxic to cattle, the ornate bella moth plays a beneficial role by eating their seeds and suppressing their reproduction.

Hosts (Back to Top)

Although a variety of plants in the family Fabaceae are listed in the literature as hosts for the ornate bella moth (Covell 2005, Robinson et al. 2010, Tietz 1972), species in the genus Crotalaria (e.g., Figures 7-10) are without a doubt the major if not the only true hosts. It is possible that the other host records are due to the habit of full-grown larvae to wander from the host plant (and often onto other species) prior to pupation.

Only four species of Crotalaria are native to the southeastern U.S. of which two occur in Florida — Avon Park rattlebox (Crotalaria avonensis DeLaney & Wunderlin), which is restricted to Florida, and rabbitbells (Crotalaria rotundifolia J.F. Gmel.). Many other species of Crotalaria were introduced into the southeastern U.S. 55-65 years ago for soil improvement and forage. Unfortunately, species of Crotalaria are toxic to livestock due to the presence of pyrrolizidine alkaloids, and are potentially fatal. Three species of Crotalaria have become established and are common in Florida. These are Crotalaria lanceolata E. Mey. and Crotalaria pallida Aiton var. obovata (G. Don) Pohill (formerly Crotalaria mucronata Desv.) which are both native to Africa and Crotalaria spectabilis Roth which is native to Asia. The name Crotalaria originates from the Greek root "crotal" which means "a rattle". It is the same root word as used in the genus name for rattle snakes, Crotalus. The mature dried fruit of Crotalaria rattles like a rattle snake when the pods are shaken or blown by the wind.

Lanceleaf rattlebox, Crotalaria lanceolata E. Mey, in fruit. This plant is a host of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 7. Lanceleaf rattlebox, Crotalaria lanceolata E. Mey, in fruit. This plant is a host of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

A flower spike of lanceleaf rattlebox, Crotalaria lanceolata E. Mey, with carpenter ants feeding at extrafloral nectaries. This plant is a host of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 8. A flower spike of lanceleaf rattlebox, Crotalaria lanceolata E. Mey, with carpenter ants feeding at extrafloral nectaries. This plant is a host of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Smooth rattlebox, Crotalaria pallida Aiton var. obovata (G. Don) Pohill (formerly Crotalaria mucronata Desv.), with flowers and fruit. This plant is a host of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 9. Smooth rattlebox, Crotalaria pallida Aiton var. obovata (G. Don) Pohill (formerly Crotalaria mucronata Desv.), with flowers and fruit. This plant is a host of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

Showy rattlebox, Crotalaria spectabilis Roth., a host of the bella moth, Utetheisa ornatrix (Linnaeus).

Figure 10. Showy rattlebox, Crotalaria spectabilis Roth., a host of the ornate bella moth, Utetheisa ornatrix (Linnaeus). Photograph by Don Hall, Entomology and Nematology Department, University of Florida.

For further information on Crotalaria species, see Isley (1990), Wunderlin and Hansen (2003), Wunderlin et al. (2016) and the Plants Database (2005).

Natural Enemies (Back to Top)

Given the opportunity, ornate bella moth larvae are cannibalistic on conspecific eggs (Bogner & Eisner 1991, Hare & Eisner 1995) and pupae (Bogner & Eisner 1992). However, cannibalism of pupae is minimized because larvae migrate off the host plant prior to pupation (Bogner & Eisner 1992).

Predators: All life stages of ornate bella moths are protected from a wide range of predators by the alkaloids sequestered from their host plants. Eggs have been demonstrated to be repellent to the spotted ladybird beetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) (Dussourd et al. 1988), the green lacewing Ceraeochrysa cubana (Hagan) (Neuroptera: Chrysopidae) (Eisner et al. 2000),and the cavity-nesting ant, Leptothorax longispinosus Roger (Now Temnothorax longispinosus [Roger]) (Hare & Eisner 1993).

Crotalaria lanceolata and Crotalaria pallida both have extrafloral nectaries that are often visited in the Gainesville, Florida area by aggressive Florida carpenter ants, Camponotus floridanus (Buckley) (Figure 8), and red imported fire ants, Solenopsis invicta Buren. Guimarães et al. (2006) reported that Utetheisa ornatrix larvae were repulsed from the racemes of Crotalaria pallida by ants attracted to the extrafloral nectaries but that predation on the larvae was rare.

Adult ornate bella moths are rejected by the wolf spider Lycosa ceratiola Gertsch (Eisner & Eisner 1991, González et al. 1999), the jumping spider Phidippus audax (Hentz) (Eisner & Eisner 1991), and the orb weaving spiders .Nephila clavipes (Linnaeus) (Eisner & Eisner 1991, González et al. 1999) and Argiope florida Chamberlin & Ivie (Eisner et al. 2005, Eisner & Meinwald 1995). They are also rejected by at least some vertebrates (e.g., the blue jay, Cyanocitta cristata [Linnaeus], and the Florida scrub jay, Aphelocoma coerulescens [Bosc]), (Eisner & Meinwald 1995), but not by the American toad, Bufo americanus Holbrook, (Now Anaxyrus americanus (Holbrook).

Parasitoids: The pyrrolizidine alkaloids do not always protect ornate bella moths from parasitoids. The eggs are parasitized by the wasp Telenomus sp. (Hymenoptera: Scelionidae) (Bezzerides et al. 2004). Also, the following six species of parasitoids have been reared from Utetheisa ornatrix pupae by Rossini et al. (2000) who reported an overall parasitism rate of 20% and suggested that pupal parasitism may be one of the chief causes of mortality in Utetheisa ornatrix:

Lespesia aletiae (Diptera: Tachinidae)
Lespesia sp. (Diptera: Tachinidae)
Chetogena claripennis (Diptera: Tachinidae)
Archytas aterrimus (Diptera: Tachinidae)
Brachymeria ovata (Hymenoptera: Chalcididae)
Consoncus (undescribed species) (Hymenoptera: Ichneumonidae)

In laboratory studies (Storey et al. 1991), the pyrrolizidine alkaloids did not protectornate bella moth eggs from infection by the entomopathogenic fungi Beauveria bassiana (Bals. Criv.) Vuill. and Paecilomyces lilacinus Thom (Now: Purpureocillium lilacinum [Thom] {Luangsa-Ard et al. 2011}).

Selected References (Back to Top)