Sleepy Orange (Eurema nicippe)

Sleepy orange
Conservation status
Least Concern (IUCN 3.1)[1]
Secure (NatureServe)[2]
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Clade:	Pancrustacea
Class:	Insecta
Order:	Lepidoptera
Family:	Pieridae
Genus:	Eurema
Species:	E. nicippe
Binomial name
Eurema nicippe (Cramer, 1779)
Synonyms
Abaeis nicippe Cramer, 1779

Eurema nicippe, the sleepy orange, is a North American butterfly in the family Pieridae. Its range spans from Central America to north along the United States-Mexico border, and it often travels further to non-mountainous regions of the southeastern United States.^[3]

This species occupies a wide range of habitats in open and disturbed environments such as roadsides, agricultural land, and scrub habitats.

In addition to its broad distribution, E. nicippe displays complex behavioral and ecological interactions such as host plant specialization and oviposition decision making based on both visual and chemical cues.

The sleepy orange is a bright orange butterfly with the upperside of the wings having wide black borders. The forewing costal margin has a small, narrow black marking that resembles a closed eye. Contrary to popular belief, its name originates from this wing patterning, rather than its behavior; the butterfly has a very rapid flight pattern when disturbed.^[4] The underside of the wings varies seasonally: summer forms are bright yellow with brick-red markings, while winter forms are browner and more heavily marked. It has a wingspan of 13⁄8–21⁄4 inches (35–50 mm).^[5]

• 
  underside (summer form)
• 
  puddling on damp ground

The sleepy orange generally prefers low elevation areas,^[3] agricultural land, and disturbed sites,^[5] and may be found in or around old fields, roadsides, woods edges, swamps, wet meadows, open woodlands, margins of ponds, waterways, and valleys.^[4]

Eurema nicippe was first described by the Dutch entomologist Pieter Cramer under the name Papilio nicippe. The species has since been placed in the genus Eurema within the family Pieridae, though some authorities categorize it under the genus Abaeis, with the current accepted binomial nomenclature being Abaeis nicippe.^[1]

Its broader phylogenetic placement has been clarified by molecular studies of the Pieridae family, with diversification rates across Pieridae correlating with temperature gradients across evolutionary time.^[6]

The sleepy orange occupies a broad range spanning Central America northward through Mexico, the southern United States, and occasionally into the northern United States during warmer months. Its permanent resident range is concentrated around Florida and Texas where adults may be found year round. The species regularly travels beyond its permanent range in summer, with records documented as far north as the Great Plains and the Upper Midwest.^[3]

The sleepy orange has the capacity for long distance dispersal with an established population existing in Hawaii which provides evidence that the species is capable of founding new populations far outside its native range.^[1]

The species generally prefers low elevation areas and is not recorded at high altitudes where terrain features such as mountain ranges restrict movement.^[1]

Its eggs are spindle-shaped and white in color when first laid, but quickly turn yellow.^[4] They are laid on the underside of the leaves of its host plant, often members of the legume family.^[7] The larva is pale green with a narrow white stripe along its length on either side and very short hairs.^[4] The chrysalis varies from pale green^[8] to brown-black later in its life cycle.^[5] They have two to four broods per year. They can be found year-round further south, but migrate north during the warmer summer months.^[9]

Eurema nicippe is multivoltine, completing two to four broods annually with breeding continuous year round in the southernmost parts of its range where temperatures remain warm.^[10]

Eggs are spindle shaped and white when first laid, turning yellow within a short time after deposition.^[11] Females lay eggs singly on the undersides of leaves of host plants, with a strong preference for members of the Fabaceae family. Females possess a pronounced ovipositional for to Phyllanthus tenellus via both visual and chemical cues when selecting egg laying sites. This ensures that newly hatched larvae are in close proximity to a suitable food source.

Larvae are pale green with a narrow white lateral stripe running along each side of the body and are covered with short hairs.^[4] They feed on the foliage of their host plants, with recorded hosts including Chamaecrista fasciculata (partridge pea), Chamaecrista nictitans (wild sensitive plant), and several Senna species including Senna hebecarpa, Senna marilandica, Senna obtusifolia, Senna ligustrina, and Senna mexicana.^[12]

The chrysalis ranges from pale green early in development to a darker brown-black coloration later in the life cycle which provides camouflage across the different substrates where pupation occurs.^[5]

Adults exhibit pronounced seasonal dimorphism. Summer form individuals have bright yellow undersides with brick-red markings, while winter form individuals are significantly browner and have a more heavily pattern.^[5] This seasonal variation reflects a state of reproductive diapause in winter adults, during which reproduction is suspended and individuals may persist for extended periods.^[5]

The common name for the Sleepy Orange derives from the small, closed-eye marking on the forewing as opposed to its movement. When disturbed, adults fly rapidly and evasively, making them difficult to approach.^[11] Adults have been observed engaging in mud puddling behavior, gathering at damp soil or the margins of waterways to extract mineral salts and amino acids from moist ground which is a common behavior among male Pieridae.^[11]

Adults take nectar from a wide variety of flowering plants and show a general preference for open, sunny habitats where flowering plants are readily accessible, including old fields, roadsides, and the margins of woodlands, swamps, and ponds. However, no strong preference for a particular nectar source has been recorded among sleepy oranges.^[3]

Females are univoltine in terms of each discrete brood, with mating and oviposition preceding the next development cycle. Males actively patrol open habitat in search of receptive females.^[13]

The sleepy orange is assessed as Least Concern on the IUCN Red Lest. It has a continuous distribution from Central America through the southern United States with a tolerance towards disturbed and agricultural habitats and stable population trends across its range.^[1] The species' multi brood reproductive strategy and broad host plant range within Fabaceae contribute to its ecological resilience.