Cabbage Looper

Trichoplusia ni — the cabbage looper — is one of the most economically important VEGETABLE PESTS in North America and one of about 35,000 species in family Noctuidae (the owlet moths — the largest family of moths on Earth). The species is widespread across all of North America from southern Canada south through the eastern and central US to Mexico, with seasonal range expansion north (the species cannot overwinter in cold northern regions and is re-established each spring by southward populations and by long-distance migration). Larvae are 3-4 cm long when fully grown, light green with thin WHITE LONGITUDINAL STRIPES along each side of the body and slightly humped midsection. Larvae have only 5 pairs of prolegs (instead of the typical 5 pairs in most caterpillars — loopers lack the central pair of prolegs that would normally be on the third and fourth abdominal segments). The reduced proleg number is the source of the species' diagnostic 'LOOPING' LOCOMOTION — caterpillars walk by drawing the rear of the body forward to meet the front (forming a loop with the body, since the missing central prolegs cannot support the body in normal walking), then extending the front body forward, repeating. The looping motion distinguishes loopers (subfamily Plusiinae) from most other caterpillar families and is a key field-ID feature. Adults are small (3-4 cm wingspan), gray-brown moths with a small distinctive SILVER COMMA-OR-FIGURE-EIGHT MARKING on each forewing — the silver mark is diagnostic for the Plusiinae and identifies cabbage loopers from above. Adults are nocturnal, fly at night, and migrate north each spring from year-round populations in the southern US and Mexico. Larvae feed on a wide range of plants but are major pests of CRUCIFEROUS VEGETABLES (cabbage, broccoli, cauliflower, kale, brussels sprouts, mustard greens) and other leafy vegetables (lettuce, spinach, beets) — major economic damage to NA vegetable production. The species is one of the most-studied LABORATORY MODEL ORGANISMS in modern entomology — used extensively in insecticide testing (the species can be reared in continuous laboratory cultures), resistance research (cabbage loopers have evolved resistance to many synthetic pesticides and are the foundational case study in lepidopteran insecticide resistance), and Bt (Bacillus thuringiensis) research (the bacterial endotoxin Bt is highly effective against cabbage loopers and is one of the most-used biological pesticides in vegetable production worldwide). The species is harmless to humans (no venom, no bite) but is a major economic pest of NA vegetable agriculture.