Plusiina

Larvae are distinguished from true geometrid loopers (Geometridae) by possessing three pairs of prolegs rather than two. Within Plusiina, species identification often requires examination of the spinneret shape—Rachiplusia nu has a differently shaped spinneret than Chrysodeixis includens. Field identification is complicated by similar larval appearance between species; R. nu older larvae tend to show darker coloration and thoracic asperites not apparent in C. includens. Adults require genitalic dissection or molecular methods for reliable species-level identification.

Associated with agricultural and natural habitats supporting their host plants. In Argentina, found in the Humid Pampas region and expanding northeastern provinces, particularly in soybean-growing areas. Dry conditions appear to favor population increases in some species.

Widely distributed across the Americas. Rachiplusia nu occurs in Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay. Chrysodeixis includens is established in the southeastern United States, Brazil, and has appeared with increasing frequency in northern Argentina. The subtribe as a whole has a predominantly New World distribution.

Larvae feed on a range of host plants including soybean, sunflower, alfalfa, and flax. Young larvae feed on lower leaf epidermis between veins, creating "window pane" damage; older larvae consume entire tissue while avoiding veins, resulting in skeletonized foliage. A single larva can consume more than 100 cm² of soybean foliage.

• Glycine max - larval food plantsoybean, major agricultural host
• Helianthus annuus - larval food plantsunflower, heavily attacked in drier western regions of Córdoba Province, Argentina
• Medicago sativa - larval food plantalfalfa, early season host for Rachiplusia nu
• Linum usitatissimum - larval food plantflax, early season host for Rachiplusia nu

Complete metamorphosis with egg, larva, pupa, and adult stages. Eggs are laid primarily on undersides of leaves. Larvae progress through multiple instars, with feeding damage increasing substantially in later stages. Specific details of pupation sites and adult longevity are not well documented in available sources.

Larvae exhibit characteristic looping locomotion due to reduced proleg number compared to typical caterpillars. Adults of at least some species (e.g., Chrysodeixis includens) hover at flowers during dusk rather than landing. Eggs are laid on leaf undersides where larvae begin feeding immediately after hatching.

Significant defoliators in agricultural ecosystems. Larval populations are suppressed by entomopathogenic fungi under moist conditions. Serve as hosts for parasitoid wasps including Cotesia vanessae, which has been investigated as a biocontrol agent.

Major agricultural pests, particularly of soybean production in South and North America. Rachiplusia nu is the primary plusiine affecting soybean in Argentina, while Chrysodeixis includens is a major pest in the southeastern United States and Brazil. Control failures occur due to misidentification and differing pesticide susceptibilities between species—C. includens has developed resistance to multiple pesticides. The subtribe has been subject to extensive research on artificial rearing diets, with the McMorran diet successfully supporting development of multiple species.

• GeometridaeTrue loopers with only two pairs of prolegs and similar looping locomotion; distinguished by proleg count and adult morphology
• Helicoverpa zeaLarval coloration and body form can appear similar, but H. zea typically has a prominent black spot above the second pair of true legs and different proleg arrangement

Frequently misidentified as Geometridae due to shared "looper" common name and similar larval movement. The subtribe name Plusiina is sometimes confused with the genus Plusia or the subfamily Plusiinae in general. Larvae of Rachiplusia nu and Chrysodeixis includens are often misidentified in areas of sympatry due to superficial similarity and difficulty of field-diagnostic characters.

• agricultural pest
• soybean pest
• looper caterpillar
• defoliator
• Noctuidae
• Plusiinae
• semilooper

• BugGuide
• iNaturalist taxon
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