Agrotis ipsilon, the dark sword-grass, black cutworm, greasy cutworm, floodplain cutworm or ipsilon dart, is a small noctuid moth found worldwide. The moth gets its scientific name from black markings on its forewings shaped like the letter "Y" or the Greek letter upsilon. The larvae are known as "cutworms" because they cut plants and other crops. The larvae are serious agricultural pests and feed on nearly all varieties of vegetables and many important grains.
This species is a seasonal migrant that travels north in the spring and south in the fall to escape extreme temperatures in the summer and winter. The migration patterns reflect how reproduction occurs in the spring and ceases in the fall.
Females release sex pheromones to attract males for mating. Pheromone production and release in females and pheromone responsiveness in males is dependent on the juvenile hormone (JH) and pheromone biosynthesis activating neuropeptide (BPAN). In the span of 2 months, the moth progresses through the life cycle stages egg, larvae, pupa, and adult. Throughout this time period, this moth faces the risk of predation and parasitism, such as by Hexamermis arvalis or by the parasite Archytas cirphis.
Description
. Antennae in male bipectinated. Forewings brown, reddish-tinged, mixed with pale greyish-ochreous, costa and sometimes median area suffused with dark fuscous; first and second lines edged with dark fuscous; spots outlined with black, reniform followed by a short black dash; subterminal line obscure, usually preceded in middle by two fine black marks. Hindwings whitish-grey or whitish, terminally suffused with fuscous. Larva ochreous brownish or bronzy-grey, sides sometimes greenish; dorsal, subdorsal, and spiracular lines faintly darker or lighter, usually darker-edged; head suffusedly brown-marked.
Geographic range
Populations of this species have been found in southern Canada, 48 of the United States (and additionally Hawaii), Mexico, Central and South America, Australia, New Zealand, the Pacific Rim, North Africa, Europe, and Asia. However, they are absent from some tropical regions and colder areas and are more widespread in the Northern than Southern Hemisphere.
This species is also known to migrate north in the spring and migrate south in the fall.
Food resources
Caterpillars
Larvae feed on weeds such as bluegrass, curled dock, lambsquarters, yellow rocket, and redroot pigweed. They will often eat all the weeds available before moving to attacking crops. Favored crops include most vegetable plants, alfalfa, clover, cotton, rice, sorghum, strawberry, sugarbeet, tobacco, and occasionally grains and grasses.
Adults
Adults feed on flower nectar. They are also attracted to deciduous trees and shrubs such as linden, wild plum, crabapple, and lilac. They are a pollinator of fetterbush lyonia.
Parental care
Oviposition
Based on the types of debris on the ground, the black cutworm prefers to oviposit in areas with fencerow (pasture) debris rather than corn field debris, woodland floor debris, and bare soil. Fencerow debris includes dry grass debris, and this may be attractive for females to oviposit early in the spring before rapid vegetation growth occurs.
After this growth, though, the moths are drawn more to low, dense plants such as the curled dock and yellow rocket. These plants have multiple stems and many low-lying basal leaves. On most plant species, the cutworm prefers to oviposit on the leaves rather than the stem.
Life history
Life cycle
In a given year, the number of generations differs based on location and weather conditions. In Canada, there are 1 or 2 generations, while in the United States, there are 2 to 4 per year. This species is abundant in warmer temperatures (such as Arkansas, US) during the late spring in May–June and early fall in September and October, while they are more abundant in cooler temperature (such as New York, US) during the summer in June and July. One life cycle lasts between 35–60 days.
Egg
The egg stage lasts 3 to 6 days. Females oviposit eggs in clusters on low-lying leaves. If such host plants are not available, the females will oviposit on dead plant material. However, they will not lay eggs on bare soil. Females can deposit eggs singly, or in groups of up to 1200 to 1900 eggs.
The nearly spherical eggs are initially white but turn brown with age. The surface of the egg possesses 35–40 ribs that radiate from one apex.