This is a medium-sized lepidopteran belonging to the Pieridae family, characterized by marked sexual dimorphism and female polymorphism. Males feature a wingspan ranging from 40 to 50 millimeters and display a vibrant bright orange coloration on the dorsal surface of their wings, bordered by a solid, thick black margin. In contrast, females present two distinct color morphs: a typical form resembling the males but with an irregular dark margin interrupted by light-colored spots, and an alba form, which exhibits a pale greenish-white or grayish hue. The ventral side of the wings in both sexes is yellowish-green, adorned with a distinct silver or discal spot ringed with reddish-brown on the hindwings, providing outstanding crypsis when the insect rests with closed wings among foliage.

Geographical distribution: This species is widely distributed across the southern cone of South America. It is highly abundant in the fertile plains of Argentina (particularly the Pampas region), Uruguay, southern Brazil (including Rio Grande do Sul and Paraná states), Paraguay, central Chile, and southeastern Bolivia. During years of population explosions, its geographic range temporarily expands into pre-Andean valleys and urbanized sectors, assisted by prevailing wind currents and localized migratory behaviors.

Habitat: It primarily inhabits open environments such as temperate grasslands, shrubby savannas, roadsides, and urban pastures. It shows a highly pronounced affinity for agricultural landscapes modified by human activities, especially forage crops. Cultivated fields of legumes constitute its optimal habitat, providing a continuous supply of host plants and flat, open spaces that facilitate flight, dispersal, and the rapid development of exceptionally high population densities.

Feeding: In the larval stage, this phytophagous insect feeds strictly on plants from the Fabaceae family. Its primary and highly preferred host is alfalfa (Medicago sativa), although it also consumes various species of clover (Trifolium repens, Trifolium pratense) and other wild legumes. Conversely, the adults are nectarivorous, utilizing their specialized proboscis to feed on the nectar of a wide array of wild and domestic flowers. They regularly visit species from the Asteraceae, Fabaceae, and Verbenaceae families, acting as secondary pollinators within their respective ecosystems.

Behavior: It exhibits highly active heliophilic behavior, flying continuously during the sunniest hours of warm, clear days. Its flight pattern is rapid, low, and erratic, which serves as an effective defense mechanism against visual predators such as birds. During cooler hours, overcast days, or at night, it roosts vertically with its wings tightly closed among low vegetation. Under specific environmental cues and high-density conditions, this species performs spectacular mass migrations, creating vast clouds of millions of individuals traveling in search of fresh feeding and oviposition grounds across rural landscapes.

Reproduction: It undergoes a complete holometabolous metamorphosis, transitioning through egg, larva, pupa, and adult stages. Following courtship, the fertilized female deposits single, spindle-shaped yellowish eggs on the upper surface of the host plant´s tender leaves. Within a few days, a bright green larva hatches, featuring a distinct white or yellow lateral stripe that perfectly mimics the host plant´s leaf veins to deter predators. After progressing through four to five instars, the mature caterpillar attaches itself to a plant stem using a silken girdle to form a greenish chrysalis. The complete life cycle takes approximately 25 to 40 days depending on ambient temperatures, allowing for multiple overlapping generations per year.

Conservation status: This insect is not currently evaluated by the International Union for Conservation of Nature (IUCN) Red List and holds no global threat status. Due to the steady expansion of agricultural land and forage monocultures in South America, its populations are highly stable and abundant. Within agricultural contexts, rather than being a species of conservation concern, it is widely managed as an agricultural pest, necessitating integrated pest management strategies to control major defoliation events in productive alfalfa fields.