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Utetheisa ornatrix
Utetheisa ornatrix
Utetheisa ornatrix
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Utetheisa ornatrix
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Superfamily: Noctuoidea
Family: Erebidae
Subfamily: Arctiinae
Tribe: Arctiini
Subtribe: Callimorphina
Genus: Utetheisa
Species:
U. ornatrix
Binomial name
Utetheisa ornatrix
Synonyms
  • Phalaena ornatrix Linnaeus, 1758
  • Utetheisa bella (Linnaeus, 1758)
  • Deiopeia ornatrix var. stretchii Butler, 1877
  • Deiopeia pura Butler, 1877
  • Deiopeia ornatrix var. daphoena Dyar, 1914
  • Deiopeia ornatrix var. butleri Dyar, 1914
  • Phalaena Tinea bella Linnaeus, 1758
  • Euprepia venusta Dalman, 1823
  • Deiopeia speciosa Walker, 1854
  • Deiopeia ornatrix var. hybrida Butler, 1877
  • Deiopeia bella var. intermedia Butler, 1877
  • Utetheisa bella var. terminalis Neumoegen & Dyar, 1893
  • Utetheisa nova J.B.Smith, 1910

Utetheisa ornatrix, also called the ornate bella moth, ornate moth, bella moth or rattlebox moth, is a moth of the subfamily Arctiinae. It is aposematically colored ranging from pink, red, orange and yellow to white coloration with black markings arranged in varying patterns on its wings. It has a wingspan of 33–46 mm. Moths reside in temperate midwestern and eastern North America as well as throughout Mexico and other parts of Central America. Unlike most moths, the bella moth is diurnal. Formerly, the bella moth or beautiful utetheisa of temperate eastern North America was separated as Utetheisa bella. Now it is united with the bella moth in Utetheisa ornatrix.

The larvae usually feed on Crotalaria species, which contain poisonous alkaloid compounds that render them unpalatable to most predators. Larvae may prey on other bella moth larvae in order to compensate for any alkaloid deficiency.

The bella moth also demonstrates complex mating strategies and is thus an excellent model to study sexual selection. Females mate multiply and receive spermatophores containing sperm, nutrients and alkaloid compounds from numerous males as nuptial gifts. Females choose males according to the intensity of a courtship pheromone, hydroxydanaidal, and carry out a sperm selection process after copulation with various males.

Distribution

[edit]

Utetheisa ornatrix is found from southeastern United States to South America (southeast Brazil). In the southeastern United States, its distribution ranges from Connecticut westward to southeastern Nebraska and southward to southern New Mexico and Florida.[1] This species is found to be more common in more tropical parts of this range, in accordance to the availability of its host plant in more southern regions.[1] It is also found throughout Mexico, South America, and Central America.[2]

Taxonomy

[edit]

In 1758, Carl Linnaeus first characterized two species of the genus Phalaena. Phalaena ornatrix was used to describe the paler moth specimens, and Utetheisa bella, described the bright pink moth specimens.[3] In 1819, Hübner moved these species to a new genus, Utetheisa.[4] For nearly a century, it was difficult to determine this moth's evolutionary history as researchers focused on external similarities (color, shape, patterns, size), rather than determining features specific to the species. This led to great confusion when trying to categorize the different subspecies.[4] In 1960, Forbes combined both species, Utetheisa ornatrix and Utetheisa bella, into the species now known as Utetheisa ornatrix.[4] His conclusion was also supported by Pease Jr. who, in 1966, used genetic testing and determined that any phenotypic differences were based on interspecific variation due to geographic differences (rather than intraspecific variation).[4]

Subspecies

[edit]
  • Utetheisa ornatrix ornatrix
  • Utetheisa ornatrix bella (Linnaeus, 1758)
  • Utetheisa ornatrix saintcroixensis Pease, 1973

Description

[edit]
On rattlebox blossom (Crotalaria sp.)

Eggs

[edit]

The eggs of the Utetheisa ornatrix are spherical in shape and range in colour from white to yellow to sometimes brown.[1]

Larvae

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The larvae are orange and brown with irregular black bands on each segment of the body. The anterior and posterior portions of the black binds are also marked with distinct white spots. Full grown larvae reach 30-35mm in length. Although most arctiid larvae have verrucae, Utetheisa ornatrix larvae lack these.[1]

Pupae

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The pupae are mostly black marked with irregular orange and brown bands. Usually, the pupae are covered with a loose layer of silk.[1]

Adult

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These moths are aposematic and use their bright coloration to warn predators of their unpalatability. Their wings range in color from yellow, red, pink, and orange to white.[2] Wings contain white bands containing six bands of irregularly spaced black spots.[5] The hind wings can be bright pink with a marginal black band. The adult Utetheisa ornatrix has a wingspan of 33 to 46 millimetres (1.3 to 1.8 in).[2]

Predation

[edit]
Mature pods of the rattlepod, Crotalaria retusa

During the larval stages, caterpillars feed on leguminous plants of the genus Crotalaria.[6] These plants contain large amounts of toxins, particularly pyrrolizidine alkaloids (PAs), which are found in high concentrations in the seeds.[6] Bella moth caterpillars sequester these toxins and use them as a deterrent for predators.[6] When the adult is disturbed, they secrete a foam containing the toxins from their head, which makes them unpalatable to predators. Since PAs are an extremely valuable resource, individual larvae compete with one another to colonize an entire pod, an elongated seed-containing pouch from the food plant.[7] Larvae that are unable to take ownership of a pod must obtain the chemicals from leaves, where they are found at much lower densities. These caterpillars sequester smaller amounts of PAs and are more susceptible to predation.[7]

Although it is beneficial to feed on seeds, larvae do not enter the pods immediately after they hatch.[8] During the first larval instars, caterpillars feed on leaves and it is not until the second or third instar that they enter the pods.[8] The evolutionary benefits of this strategy are not understood.[8] When caterpillars metamorphose into adult moths, they carry the alkaloids with them, which continue to protect them during the adult stage.[6]

PAs render the bella moth unpalatable to many of its natural enemies like spiders and insectivorous bats.[9][10] Spiders that capture bella moth larvae or adults release them soon after, leaving them unharmed.[10] In contrast, bella moth individuals grown on a PA-free diet are readily preyed on by spiders.[10] Similarly, bats that catch bella moth individuals quickly release these unpalatable moths without harming them.[9] Unlike other moths of the Arctiidae, the bella moth does not possess an acoustic aposematism system that would enable it to avoid bats altogether.[9] Bella moth larvae and some predators like loggerhead shrikes are not negatively affected by PAs.[6]

The bella moth is able to detoxify PAs due to the possession of the gene pyrrolizidine-alkaloid-N-oxygenase.[11] It has been experimentally shown that bella moth larvae upregulate the expression of this gene when the amount of PAs in their diet increases.[11] In addition, it has been shown that PA rich diets do not have a negative effect on the fitness of these moths,[11] but only affect time of development, which increases with increasing PA concentration in diet.[11] However, caterpillars with longer development times reach similar pupal sizes compared to those with shorter developmental times due to diets containing smaller amounts of PAs.[11]

Cannibalism

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On occasion, bella moth caterpillars cannibalize other eggs, pupae or larvae from the same species.[12] Since PAs are a limited resource, some caterpillars do not reach optimal levels and resort to cannibalism.[13] This behavior is a consequence of PA deficiency rather than hunger, since deficits in alkaloids are the main cause of mortality.[12] Pupae cannibalism is rare because larvae normally pupate far away from the plant where they feed.[12] Egg cannibalism is also rare because eggs provide larvae with very small quantities of PAs[13] and because eggs from the same cluster hatch synchronously.[14] Larvae may also feed on other bella moth larvae that are laden with alkaloids.[12] This is more common since feeding on one single larva is sufficient to compensate for the cannibalistic caterpillar's alkaloid deficiency.[12]

Kin recognition

[edit]

Bella moth caterpillars may have the ability to recognize other larvae as kin, as larvae are less likely to intrude upon siblings than non-siblings established in seedpods.[15]

Mating

[edit]

Bella moths of both sexes use very complex reproductive strategies, making this species an excellent model system for studying sexual selection.[7] Females mate multiple times over their three- to four-week lifespan as adults.[7] They mate with an average of three to five males, each of whom provides her with a nuptial gift, a spermatophore containing sperm, nutrients, and alkaloids.[7] Adult males invest up to 11% of their body mass to create a spermatophore they provide to a female during mating.[7] The nutrients given in the spermatophore allow the female to produce, on average, an additional 32 eggs.[16]

Mating system

[edit]

The bella moth presents a polyandrous mating system, where females mate with multiple males.[17] On average, females mate with three to five males over their lifespan of three to four weeks but can mate with and receive up to thirteen spermatophores.[17] Since spermatophores contain nuptial gifts of pyrrolizidine alkaloid (PA) and nutrients, multiple mating helps the female increase the fitness of her offspring.[17] In addition, multiple mating also benefits the female directly. Since the spermatophores are sizeable and can be digested within the female, multiple mating allows females to accrue the resources necessary to build additional eggs.[17] This is equivalent to a 15% increase in egg production.[18] In addition, multiple mating results in increased transmission of alkaloidal gifts to eggs.[19] This provides protection to the eggs against predation.[17] However, this does not mean that there is segregated allocation of these gifts. Instead, the PA obtained from numerous males is allocated in admixture so that eggs tend to receive from more than one male source.[19] In contrast, normally most of the sperm used to fertilize the eggs comes from a single male.[16]

Courtship

[edit]

Courtship begins at dusk.[20] Stationary females release a sexual pheromone that lures males.[20] They emit these chemicals in short pulses to provide close-range orientation cues to male moths as they seek out the females.[21] When a male reaches a female, he flutters around her and thrusts two peculiar tufts of scales from his coremata, two yellow spherical structures by the male's genital organs.[6][22] By doing so, the male emits a specific scent from his coremata that is attributed to a pheromone, hydroxydanaidal.[20] After receiving the scent, the female proceeds to mating.[22]

Copulation lasts for up to 12 hours.[23] It takes the male about two hours to transfer the spermatophore containing all of the sperm and nutrients he is going to offer to the female.[24] The remaining hours of copulation are exclusively used for alkaloid transfer.[24] These alkaloids distribute themselves evenly around the female body, even the wings, and offer her great protection as they render her unpalatable to most predators.[24] Eventually, the female allocates about one third of the alkaloids she receives to her ovaries, where they will be used to confer protection to the eggs.[24]

Female pheromonal chorusing

[edit]

Bella moth mating behavior is exceptional in that females compete with other females to obtain more males, as opposed to males competing with males.[25] As in many other moth species, females release sexual pheromones that males can detect over long distances.[25] However, in most species, females do not interact with one another during pheromone release.[25] Female bella moths are unique in that females from the same family often engage in collective pheromone release termed “female pheromonal chorusing”.[25]

This phenomenon is a consequence of a female-biased operational sex ratio. This means that at any given time, there are more females than males seeking to copulate.[25] This occurs because males lose up to 11% of their body mass during mating and once they are done mating, they need time to sequester resources that will allow them to deliver a spermatophore to the next female they mate with.[25] On the contrary, females do not need time to prepare for their next copulation.[25] Due to the unequal mating rates, males become valuable to females and female-to-female competition rises dramatically as a consequence.[25]

Engaging in pheromonal chorusing allows females to increase the attractiveness of genetic relatives and increase their indirect fitness.[25] Females may also, but less frequently, engage in female chorusing with unrelated females.[25] It has been suggested that chorusing is still beneficial under these circumstances, because cooperation for pheromone release may increase the attractiveness of the entire group and increase each moth's individual fitness.[25] It has been experimentally shown that when females detect other female pheromones they increase the rate of pheromone release and call for longer periods of time.[26] Such observations support the hypothesis that females cooperate with one another to increase mating success.[26]

Sexual selection

[edit]

Precopulatory

[edit]

Although most female moths mate multiply, very low instances of mixed paternities occur.[16] In fact, most progeny in a single clutch is sired exclusively by one male.[16] Females of this species do not select based on age, mating order, between-mating interval, or duration of copulation.[16] Instead, female Utetheisa ornatix demonstrate female choice in mate selection that depends on body size, systemic content of defensive pyrrolizidine alkaloid, and glandular content of the courtship pheromone hydroxydanaidal.[27] Selecting for these males provides the females with multiple benefits such as obtaining sperm packages with more defensive pyrrolizidine alkaloids which results in larger offspring.[18] Offspring fathered by larger males are generally less vulnerable to predation because of their higher alkaloid content, allowing the offspring to have higher viability and fitness.[18]

Larger males with the highest alkaloid content can be distinguished by a specific pheromonal scent that predicts the content of the alkaloidal gifts: hydroxydanaidal (HD).[20] There is a relationship between the size of the male, the type of food the males fed on as larvae, and the composition of its spermatophores.[20] For example, males that fed inside a seed pod rather than on leaves produce higher levels of HD.[20] In addition, these males have higher adult weights and have higher systemic loads of PA, the metabolic precursor of HD.[20] By selecting for HD-rich males, the female moth ensures the receipt of a large alkaloid gift (phenotypic benefit) and genes that encode for large size (genetic benefit).[27]

The female's mating preference is inherited paternally since the preference gene or genes lie mostly or exclusively on the Z sex chromosome.[28] The preferred male trait and the female preference for the trait are strongly correlated; females with larger fathers have a stronger preference for larger males.[28]

Postcopulatory

[edit]

After copulating with several males, rival sperm carried by a female do not compete directly for access to the eggs.[16] Females direct a postcopulatory selective process where they choose male sperm based on the intensity of the courtship pheromone that was released prior to copulation, hydroxydanaidal (HD).[7] The intensity of this signal is directly proportional to the amount of alkaloids sequestered by the moth during the larval stages.[7] As a consequence, this pheromone is an indirect indicator of success during larval development and will ultimately determine which sperm will be passed on to the offspring.[7] Once they have selected a male, females use their musculature to channel the selected sperm through the chambers and constructs of their reproductive systems to their eggs.[16]

Parental investment

[edit]

The eggs of the bella moth contain pyrrolizidine alkaloids (PAs) that the mother delivers.[29] The alkaloid is stored during the larval stages and retained through metamorphosis, protecting both larvae and adults from predators.[29] Female moths receive alkaloids from the males at the time of mating as part of the spermatophore.[29] Although the male's contribution of PAs is less than that of the female, it still contributes significantly to egg protection.[29]

Spermatophore

[edit]

The spermatophore that males give to the females when mating contains sperm, nutrients, and pyrrolizidine alkaloids (PA), and accounts for up to 11% of the male's body mass.[18] PA plays an important role in preventing predation in Utetheisa ornatrix because it is poisonous to most organisms. Males transmit PA to the females via a sperm package; the females then give this mating gift to the eggs,[30] along with their own alkaloidal supplement and is utilized to protect the offspring from predation.[18] In addition, females also personally benefit from the gift through protection and nutrition. After mating with a PA-rich male, the received PA is quickly allocated to all body parts.[30] As a result, females become and remain unacceptable as prey to numerous organisms such as spiders.[30] Another problem that females face is the risk of incurring a PA deficit due to the large amount of eggs they lay. Spermatophores is one way for females to compensate for this loss in PA.[19]

Host plants

[edit]
Crotalaria pallida

Plants of the genus Crotalaria are the major hosts for the Utetheisa ornatrix, although a variety of plants in the family Fabaceae have also been cited in literature.[1] The word Crotalaria originates from the Greek root “crotal,” which means “a rattle” and is characteristic of the pods found on these plants.[1] The Crotalaria host plants contain pyrrolizidine alkaloids, which are used by the Utetheisa ornatrix to repel predators.[1] Specific host plants used include:

  • Crotalaria avonensis (Avon Park rattlebox)
  • Crotalaria rotundifolia (rabbitbells)
  • Crotalaria lanceolata
  • Crotalaria pallida (smooth rattlebox)
  • Crotalaria spectabilis (showy rattlebox)
  • Crotalaria retusa[1]

Pyrrolizidine alkaloids and humans

[edit]

Pyrrolizidine alkaloids (PAs) are the toxins the bella moth is able to ingest and use for protection from predators.[1] They are known to be the principal toxins found in plants that can cause disease in humans and other animals.[31] Reported pathways for human exposure include crop contamination, milk and honey contamination and some traditional herbal medicines.[31] Once ingested, the alkaloids affect mainly the liver and the lungs. Human poisoning can cause veno-occlusive disease and teratogenicity.[31]

References

[edit]
[edit]
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Utetheisa ornatrix

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from Grokipedia
Utetheisa ornatrix, commonly known as the ornate bella moth or rattlebox moth, is a strikingly colored species of tiger moth in the subfamily of the family , characterized by its pink or yellow forewings marked with rows of black spots ringed in white and pink hindwings bordered in black, with a of 33–46 mm. Native to the , it ranges widely from southern through eastern to , extending southward through and to and , and is known for its migratory behavior, with adults capable of long-distance flights and lifespans up to 50 days. The ' life cycle is closely tied to host in the genus (), particularly rattlebox species containing toxic pyrrolizidine alkaloids, which larvae sequester for against predators and for producing pheromones in adults. Eggs are laid in clusters on host foliage, and the gregariously feeding caterpillars, which are orange or yellow with black bands, develop through several instars before pupating in sheltered locations such as under bark or in debris. Adults primarily feed on and exhibit in pheromone production, with males releasing (R)-hydroxydanaidal derived from larval-acquired alkaloids as a pheromone during elaborate displays to stimulate receptive females. This moth's dependence on —both native and introduced —has ecological implications, as it can influence plant distribution and serve as a in studies of and migration.

Taxonomy

Classification

Utetheisa ornatrix belongs to the kingdom Animalia, phylum Arthropoda, class Insecta, order , family , subfamily , genus Utetheisa, and species U. ornatrix. The species was first described by in 1758 as Phalaena ornatrix. The specific epithet "ornatrix" derives from the Latin word for a female adorner or , alluding to the moth's elaborately patterned and colorful wings. Historically, the taxon was classified within the family Arctiidae, which was elevated to a subfamily () within following a major revision of Noctuoidea higher classification. Linnaeus initially described two similar forms as separate : the paler Phalaena ornatrix and the more vividly colored Phalaena bella, both later transferred to the genus Utetheisa by Jacob Hübner in 1819. In 1960, William T. M. Forbes synonymized Utetheisa bella with U. ornatrix based on observed color variation and consistent genitalia, resolving them as a single polymorphic . This synonymy has been supported by post-2000 DNA barcode analyses indicating no significant between the forms, treating them as variants within U. ornatrix. Accepted synonyms include Phalaena ornatrix Linnaeus, 1758, and Phalaena bella Linnaeus, 1758.

Subspecies

Utetheisa ornatrix is recognized as comprising three : the nominal U. o. ornatrix, U. o. bella, and U. o. saintcroixensis. The U. o. ornatrix is associated with tropical and southern , characterized by cream-white forewings featuring a discal spot and marginal black spots, along with white hindwings lacking extensive patterning. The subspecies U. o. bella occurs across North and , from northward to and . Originally described as a distinct by Linnaeus in 1758, it was later synonymized with U. ornatrix following analyses and the absence of genitalic differences, as detailed in taxonomic revisions from the early . Morphologically, U. o. bella is distinguished by its vivid hindwings and forewings bearing six vertical rows of black-and-white spots. U. o. saintcroixensis is restricted to the , particularly St. Croix in the , and was described by Pease in 1971 based on specimens exhibiting variation in wing patterning. This shows reduced spotting on the wings relative to continental forms and is thought to result from hybridization events in the region. Genomic studies from the and , including analyses of over 100 specimens, confirm subspecific differentiation across these taxa through genetic structure and regulatory genes like cortex (influencing forewing spots) and lim3 (linked to hindwing color), without evidence of complete .

Distribution and Habitat

Geographic Range

Utetheisa ornatrix is native to eastern , where its range extends from westward to southeastern and southward through , , , and . The species' distribution continues seamlessly through and into , reaching as far south as southeastern and . Within its North American range, U. ornatrix exhibits higher abundance in tropical and subtropical regions, correlated with the greater availability of its primary host plants in the genus Crotalaria. In contrast, populations are more sporadic in the northern United States, with occasional vagrant records extending into southern Canada. Recent observations from 2000 to 2025, documented through platforms such as and LepNet, suggest a slight northward extension of the species' range in the United States, potentially attributable to climate warming trends that expand suitable conditions.

Habitat Preferences

_Utetheisa ornatrix inhabits open, herbaceous environments including fields, coastal dunes, savannas, flatwoods, sandhills, and disturbed areas that support its host plants. These habitats are typically found at elevations from up to about 1,500 m, with records in coastal lowlands and mountainous regions exceeding 1,200 m. The species occurs across subtropical to temperate regions, favoring areas with warm summers that allow for multiple generations annually. Larvae develop preferentially in proximity to clusters of host plants within these open or semi-open settings, where they can access foliage for feeding and sequestration of defensive compounds. Adults, being diurnal fliers, are active in sunny, vegetated margins of fields and dunes, where they on flowers and engage in behaviors during daylight hours. This preference for sun-exposed areas aligns with their conspicuous aposematic coloration and daytime activity patterns. The thermal requirements for development influence suitability, with a lower developmental threshold of approximately 13.8°C for the egg-to-adult cycle and an optimal temperature range of 18–30°C supporting high viability across life stages. Populations thrive in climates permitting sustained warm periods, enabling 3–13 generations per year depending on regional isotherms, though viability declines above 32°C. These conditions are consistent with observations in southern U.S. states and tropical regions where is established.

Migration Patterns

_Utetheisa ornatrix exhibits migratory behavior consistent with patterns observed across the Utetheisa genus, characterized by significant between populations. Genomic analyses of approximately 100 specimens reveal three main population clusters—western , eastern , and /—with evidence of ongoing admixture driven by dispersal. This is indicative of seasonal southward movements from the to and , reflecting the species' tropical origins and northward colonization history. Higher in populations further supports this dynamic, with lower diversity in the western U.S. suggesting more recent establishment through migration. Migration in U. ornatrix appears facultative, with adults undertaking northward flights in and , while breeding occurs continuously in southern regions. Two primary migratory pathways facilitate range expansion: a continental route and an island-hopping path via the from to the U.S. In northern non-breeding areas, adults are observed primarily as vagrants or strays, occasionally reaching as far as , which underscores the species' dispersive capabilities despite unstable populations in some areas like . Compared to Old World congeners such as U. lotrix and U. pulchella, which demonstrate more extensive intercontinental migrations across large bodies of water and islands, the migratory tendencies of U. ornatrix are less pronounced but still substantial within the . Recent citizen science data from platforms like corroborate these patterns, documenting stray occurrences in northern latitudes during the 2020s and highlighting the role of dispersal in maintaining population connectivity.

Description

Eggs

The eggs of Utetheisa ornatrix are spherical, measuring 0.5–0.7 mm in diameter. They appear pale yellow or creamy when freshly laid but darken to brown or black near hatching. Eggs are deposited in clusters of 10–50, typically on the undersides of leaves shortly after mating. Oviposition site selection is influenced by the female's (PA) content, which promotes preference for PA-rich host plants. Egg development requires 3–8 days for incubation, varying inversely with (e.g., 4.5 days at 25°C and 3 days at 32°C), under conditions of 18–30°C. No occurs in this stage.

Larvae

The larvae of Utetheisa ornatrix exhibit aposematic coloration, featuring an orange-brown body with broad irregular black bands across each segment and distinct white spots on the anterior and posterior margins of these bands. This patterning warns potential predators of the larvae's chemical defenses derived from host plant toxins. At maturity, larvae measure 30–35 mm in length. Larval development typically involves 5 instars, though the number can vary slightly under different conditions. Early instars are highly gregarious, , , and migrating as cohesive groups on host plant foliage. In contrast, later instars tend to disperse, adopting a more solitary or forming small groups while targeting seed pods. The total duration of the larval stage varies with , ranging from approximately 17 days at 32°C to 56 days at 18°C in settings; at an optimal of 25°C, development averages 26.5 days when reared on artificial diet. U. ornatrix larvae are polyphagous within the family but show a strong preference for species, initially feeding on leaves in early instars before shifting to unripe seed pods in later stages. This feeding strategy allows them to sequester pyrrolizidine alkaloids from the plants, which are incorporated into their tissues for defense (see Pyrrolizidine Alkaloids section for details).

Pupae

The pupal stage of Utetheisa ornatrix represents the metamorphic phase following larval development, during which the undergoes complete transformation within a protective . The pupae are distinctly colored black with irregular orange-brown bands and are encased in a loose silken cocoon spun by the mature . This morphology provides some and protection in natural environments, with the layer offering minimal but essential shielding against environmental factors and minor predators. The duration of the pupal stage varies primarily with temperature, typically lasting 10.3 days (SD ± 0.96) at 25°C under conditions on an artificial diet, with viability rates around 91%. Across a broader range of 18–32°C, development time extends from 6.3 days at higher temperatures to 24.1 days at cooler ones, reflecting the species' sensitivity to environmental cues that influence metabolic rates. Mature larvae select pupation sites by migrating away from the host plant to concealed locations, where they spin their cocoons in sheltered microhabitats such as leaf folds, , ground , under loose bark on nearby trees, or within thick and debris. This dispersal behavior reduces exposure to host-specific threats and enhances concealment. There is no parental guarding of pupae, as adult females do not exhibit post-oviposition care, leaving the immobile pupae reliant on site choice and inherent defenses for survival.

Adults

The adult Utetheisa ornatrix, commonly known as the ornate bella moth, exhibits a ranging from 30 to 45 mm. The forewings display variable coloration, typically or pinkish with transverse bands containing rows of spots, while the hindwings are bright with an irregular marginal band. Two main color forms are recognized: the common "bella" form with forewings and hindwings, and a paler "ornatrix" form found in southern and . This striking pattern contributes to the moth's overall appearance, making it one of the most conspicuous arctiid moths in its range. Sexual dimorphism is evident in body size, with males generally larger than females, a reversal of the typical lepidopteran trend where females are often larger. Males also tend to have higher concentrations of courtship pheromones correlated with their body mass, though both sexes share the same aposematic coloration for visual signaling. Visual differences between sexes are minimal beyond size. Unlike most moths, adult U. ornatrix are diurnal, actively flying during daylight hours, particularly in warm sunlight, which facilitates their visibility and foraging on nectar sources. This daytime activity pattern distinguishes them from nocturnal relatives and aligns with their bold coloration. Adults typically live for about three weeks, during which they focus on feeding and dispersal. Their aposematic appearance serves a warning function against predators, as detailed in defenses against predators.

Chemical Ecology

Pyrrolizidine Alkaloids

Pyrrolizidine alkaloids (PAs) play a central role in the chemical of Utetheisa ornatrix, serving as acquired defensive compounds and precursors for reproductive signals. Larvae obtain these toxins by feeding on host plants in the genus , such as C. spectabilis, which contain PAs including monocrotaline as a principal component. Within the moth, monocrotaline undergoes conversion to hydroxydanaidal, a key courtship released by males from coremata during mating displays. Once acquired, are sequestered primarily in the and specialized integumental glands, where they accumulate to concentrations reaching up to approximately 3% of the moth's dry body weight. This storage enables dual functions: toxicity that deters predators and provision of precursors that signal male quality to females during courtship. The alkaloids are maintained in a non-toxic N-oxide form in these tissues, minimizing harm to while preserving their defensive potency. U. ornatrix lacks the capacity for de novo PA biosynthesis and instead relies on dietary uptake followed by metabolic modification. Plant-derived PAs, such as monocrotaline, are transformed through enzymatic in the moth's tissues, yielding derivatives like hydroxydanaidal without independent synthesis of the core structure. Studies, including recent genetic analyses from 2024 identifying genes involved in PA and conversion, have reinforced that this sequestration-and-modification strategy is obligatory, with no evidence of endogenous PA production in the .

Host Plants

Utetheisa ornatrix primarily utilizes in the genus Crotalaria (family ) as host plants for larval feeding and adult oviposition. Key species include the native C. avonensis, C. rotundifolia, and C. pumila, as well as introduced species such as C. pallida, C. retusa, C. lanceolata, and C. spectabilis. These provide essential pyrrolizidine alkaloids (PAs) that the larvae sequester for defense. Larvae of U. ornatrix begin by feeding on the foliage of plants, often leading to significant defoliation, before migrating to unripe seed pods where they bore in to consume the - and PA-rich . This seed-feeding accelerates larval development and results in larger adult moths compared to foliage-only diets. Adults preferentially oviposit on these host plants, thereby linking their to availability. The PA content in Crotalaria hosts varies by species and plant part, with immature seeds containing up to five times more PAs than foliage; for instance, C. spectabilis exhibits notably high PA concentrations in both leaves and seeds, influencing larval growth and defense efficacy. Host plant distribution plays a critical role in limiting the geographic range of U. ornatrix, with the most prevalent in regions where Crotalaria species abound; the introduction of invasive exotic Crotalaria has facilitated the 's expansion across the by providing abundant, reliable resources.

Predation

Defenses Against Predators

_Utetheisa ornatrix employs as a primary visual defense, with both larval and adult stages displaying conspicuous warning coloration to deter predators. Larvae exhibit an orange-brown body accented by broad, irregular bands across each segment, signaling their to potential threats. Adults feature bright orange, , or forewings crossed by transverse bands and dotted with spots, enhancing visibility during flight and further advertising their unpalatability. This bold patterning aligns with the species' reliance on chemical defenses derived from pyrrolizidine alkaloids (PAs), which are sequestered during the larval stage from host plants. Physiological defenses center on toxicity mediated by PAs, which render the moth unpalatable and actively repellent to a range of predators. When disturbed, adults emit a frothy laced with PAs from the anterolateral margins of the , often in two bubbling masses that serve as a direct chemical barrier. This regurgitation-based response deters immediate attack, as the foam's prompts predators to release the moth. Experimental evidence from the demonstrates high efficacy against arachnids; for instance, alkaloid-laden adults were rejected in 100% of trials by ( ceratiola), compared to 100% acceptance of alkaloid-free controls. Similar protection extends to orb-weaving spiders ( clavipes), with PA-containing individuals consistently rejected. Behavioral adaptations complement these chemical and visual strategies to minimize predator encounters. Unlike most moths, Utetheisa ornatrix is diurnal, actively flying during daylight hours, which reduces exposure to nocturnal predators such as bats and many spiders. Larvae further mitigate risks through brief during aggregation, allowing siblings to cluster in ways that dilute individual predation pressure without promoting intraspecific attacks.

Cannibalism

Cannibalism in Utetheisa ornatrix primarily involves larvae consuming eggs or younger conspecifics, serving as an adaptive strategy to acquire nutrients and pyrrolizidine alkaloids (PAs) essential for defense. Laboratory experiments demonstrate that newly hatched or early instar larvae readily cannibalize eggs when presented with clusters, with PA-deficient individuals showing the highest propensity for this behavior. In one such study, PA-deficient larvae preferentially targeted PA-laden eggs over PA-free ones, indicating that alkaloid supplementation drives the act rather than mere hunger. Triggers for cannibalism include systemic PA deficiency, often resulting from feeding on low-quality host plants lacking sufficient alkaloids, as well as potential resource competition under crowded conditions. This behavior allows deficient larvae to replenish their PA stores, enhancing survivorship against predators, though it may also provide general nutritional benefits during periods of scarcity. While pupal cannibalism occurs similarly in lab settings for PA gain, it is rarer in nature due to larvae pupating away from host plants. Field observations from the and reveal cannibalism rates of approximately 3% across monitored egg clusters on host plants, with instances more frequent in mixed or non-kin aggregations where discrimination does not occur. In laboratory assays simulating these conditions, up to 30% of larvae engaged in preferential consumption of available eggs over 72 hours, highlighting elevated rates under controlled PA-limited or crowded scenarios. Overall, this intraspecific predation helps regulate by reducing sibling for limited PA-rich resources.

Kin Recognition

In Utetheisa ornatrix, larval manifests during competitive interactions over resources such as seedpods, where exhibit reduced aggression compared to non-kin, thereby minimizing the risk of among relatives. Experimental contests revealed that resident larvae were more likely to retain control of contested seedpods when facing intruders (68% success rate) than non- intruders (48% success rate), indicating a toward tolerating kin and directing competitive efforts toward unrelated individuals. This preference effectively lowers the incidence of kin cannibalism by decreasing the intensity of confrontations within family groups. The mechanism underlying this discrimination appears to rely on olfactory cues, potentially involving chemical profiles acquired early in development, such as through imprinting on eggs or conspecific odors during . While cuticular hydrocarbons serve as signals in many , their specific role in U. ornatrix larvae remains inferred from behavioral patterns rather than direct chemical analysis. These cues enable larvae to assess relatedness in dense clusters, where high densities are common due to clustered oviposition by females. This behavior confers an evolutionary advantage by safeguarding , as sparing siblings enhances the propagation of shared genetic material in a species prone to intraspecific predation. In larval clusters, also facilitates collective benefits from pyrrolizidine alkaloids () sequestered from host plants, promoting group-level protection without the costs of . Recent studies affirm the persistence of this chemically mediated recognition, building on foundational behavioral observations from the late that highlighted olfactory influences in larval interactions.

Reproduction

Mating System

The mating system of Utetheisa ornatrix is polygynandrous, characterized by high levels of in both sexes, with females exhibiting pronounced by an average of 3 to 5 times over their 3- to 4-week adult lifespan and up to 13 times in some cases. Each copulation delivers a from the male, which includes not only but also substantial nutrients and pyrrolizidine alkaloids that enhance by about 15% per and provide chemical protection to her eggs. Males are also promiscuous, multiple times across their lifespan, but face significant constraints due to a post- refractory period of 6 to 7 days needed to replenish a full-sized , which can represent up to 11% of the male's body mass and thus constitutes a heavy per-copulation . Laboratory observations indicate balanced but temporally staggered reproductive opportunities for males and females. The primary sex ratio is near 1:1, assuming equal developmental lifespans for males and females, but the operational sex ratio becomes female-biased because of the males' extended refractory period, intensifying female intrasexual competition for mates. Encounters are facilitated by adult aggregations around host plant patches, such as those of Crotalaria species, where clustered individuals create dense, pheromone-mediated signaling environments that elevate mating rates. This spatial concentration around resources contributes to the system's efficiency despite the sex ratio dynamics.

Courtship

The courtship of Utetheisa ornatrix involves a series of precopulatory interactions primarily driven by male displays and female sensory evaluation. Males are attracted to calling females by the female's pulsed sex attractant , Z,Z,Z-3,6,9-heneicosatriene, and upon approaching, the male everts a pair of brush-like glandular structures known as coremata from his abdomen. These coremata contain and release the male's , hydroxydanaidal, which is derived from pyrrolizidine alkaloids sequestered during the larval stage from host plants. To disseminate the , the male fans his wings while positioning the coremata near the female's antennae, allowing her to assess its quality and quantity through direct antennal contact. This assessment enables the female to evaluate the male's content, which signals his ability to provide protective chemicals in the upcoming nuptial gift. If the male is deemed suitable, the female responds by raising her wings to expose her , facilitating the male's mounting and subsequent copulation; rejection typically involves the female extruding her or fleeing. spreading by the male is a key visual and olfactory component of the display, emphasizing the coremata's exposure. These rituals occur in the vicinity of host plants such as species, where adults aggregate, though the species exhibits diurnal flight activity overall, with peak mating interactions taking place crepuscularly, approximately 1 to 1.5 hours after sunset. Field observations indicate that courtship success varies with male pheromone titer, correlating with body size and larval diet quality, though specific rates are influenced by environmental factors like plant availability.

Pheromonal Communication

In Utetheisa ornatrix, males produce the courtship hydroxydanaidal, derived from pyrrolizidine alkaloids (PAs) sequestered during the larval stage from host plants such as Crotalaria species. This compound is released through eversible coremata, glandular structures in the male's abdomen that are deployed during close-range interactions with females, signaling the male's possession of protective alkaloids and inducing female receptivity by prompting behaviors such as wing raising. The operates effectively over short distances, facilitating mate assessment once males have approached calling females. Females of U. ornatrix engage in pheromonal chorusing, a synchronized communal display where groups of females coordinate the release of their , Z,Z,Z-3,6,9-heneicosatriene. In laboratory studies, clustered females initiate signaling earlier in the scotophase, exhibit fewer interruptions, maintain longer calling bouts, and increase abdominal pumping rates (1.5–3.0 s⁻¹) compared to solitary individuals, collectively amplifying the plume's intensity and persistence. This behavior, documented in a 2007 field-confirmed investigation, enhances male detection and arrival rates by creating a more prominent attractant signal, as evidenced by higher mating frequencies in grouped versus isolated females. Pheromonal chorusing serves to improve mate location in sparse populations, where U. ornatrix adults aggregate near host plant patches like Crotalaria stands, allowing the amplified signal to draw males from greater effective ranges. Additionally, grouping may reduce individual predation risk through the dilution effect, as predators such as bats or spiders are less likely to target any single female amid the cluster, though this benefit remains inferred from observational data.

Sexual Selection

In Utetheisa ornatrix, precopulatory sexual selection primarily involves female choice of males based on the intensity of the courtship pheromone hydroxydanaidal, which is derived from pyrrolizidine alkaloids (PAs) sequestered during the larval stage. This pheromone, emitted from male coremata during courtship, signals the male's PA load, with higher concentrations eliciting stronger female acceptance responses, such as wing raising, thereby increasing mating success. Females also assess male body size and courtship vigor, both of which positively correlate with PA content and overall male quality, allowing females to select partners that can provide superior protective resources. Postcopulatory occurs through mechanisms of , where females mate multiply and receive spermatophores from successive males, but paternity is biased toward the of larger males with higher PA loads. Spermatophore size, which scales with male body size and PA investment, influences the proportion of eggs fertilized, as females selectively utilize from these larger gifts, independent of order or copulation duration. This bias reinforces precopulatory preferences by favoring the genetic and nutritional contributions of high-PA males. The adaptive benefits of this drive the of PA sequestration traits, as selected males transfer PAs via spermatophores that protect both the female and her eggs from predators. Offspring inherit not only these protective alkaloids but also heritable genetic components of PA sequestration efficiency, enhancing their survival and sequestration ability, as demonstrated in genetic analyses linking male signals to offspring fitness.

Spermatophore

The spermatophore of Utetheisa ornatrix is a gelatinous packet comprising over 10% of the male's body mass on average. It consists of , nutritive substances, and pyrrolizidine alkaloids (PAs) sequestered by the male from his larval diet. During copulation, which lasts 6–12 hours, the male transfers the to the female's copulatrix. The female digests the packet post-mating, converting its nutrients into energy for egg production and incorporating the PAs into her eggs for . This nuptial gift boosts female reproductive output by supplementing her resources, thereby increasing oviposition rates and viability. Males possessing greater PA reserves produce larger spermatophores with proportionally more contents.

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