Dark Sword-grass Agrotis ipsilon
Reaching a wingspan of 40 to 50 mm the Dark Sword-grass is lightly bigger than the other Agrotis species in Britain. The species can be told apart by the "i" in the wings. But the best way to tell it apart is by looking at the posure when in rest. The wings are very much put on top of each other. Thus the animal looks very slim and not like a typical owlet moth at all. Near the top of the wing is a light patch showing some dark long triangles. Near the base of the wing it is less clearly marked and rather drab.
The Dark Sword-grass is a very common migrating species, present all over the world. In summer it will travel great distances and even is reported from Iceland and above the polar circle and from New Zealand. In most of these cooler parts, including most of Western Europe, it doesn't breed. Where it does breed, e.g. Southern Europe and central parts of the USA, it may become a great pest. The larvae are known as Cut Worms. Later instars eat their host plants at ground level. The plants become detached from their roots and die. The Dark Sword-grass has a wide range of host plants, such as alfalfa, clover, cotton, rice, strawberry, sugarbeet, grains and grasses. It will happily breed in fields and farms, but in the wild as well, making it very difficult to fight. And even when coped with rather successfully migrating moths will reinvest fields.
The white eggs are deposited on leafs in clusters. The caterpillars appear very soon: the eggs hatch after 3 to 7 days! The caterpillars are blackish, brownish or greyish and have a brown head with many black spots. During the first part of his life the caterpillar will feed on foliage and remain above ground in the host plant. Little damage is done in these first four stages. From the fourth instar onwards the caterpillar will hide underground during the day. During the night they feed on ground level. Full grown larvae will reach some 50 mm. The larvae then goes underground to pupate. Pupation takes only 2 to 3 weeks. The Dark Sword-grass has one to three breeds a year, depending on the temperature.
This species is known world wide. It breeds in warmer climates, except for a few regions in the tropics, but migrates world wide and is known from Australia to Hawaii, in most parts of Asia, the Americas, Africa and Europe. Breeding in Britain and other parts of Western Europe has never been proven and is unlikely. Appears in Britain every year and is most numerous from August to October. Large numbers are seen in the South, but animals do appear in Scotland and Ireland as well. This species is attracted to flowers, sugar and light, but flies at night exclusively.
The Dark Sword-grass is known as the Black Cutworm in the USA.
