This moth is out in June and July; and during the latter month lays its eggs on the elder (Sambucus nigra), and the various low plants that supply the larva with food.
The larva is greenish or greyish, sometimes with a reddish tinge, with a light line down the back. The twelfth segment is humped, and there are dark V-shaped marks on the back of segments five to twelve inclusive. It is full grown in September, and burrows into the ground to undergo its change to the chrysalis, in which state it remains throughout the winter.
The Rustic Shoulder-knot (Apamea basilinea)
The fore wings of this species are pale ochreous grey, with light brown markings; and there is a short dark streak in the middle of
the base, from which feature the specific name (Basilinea) is derived. The hind wings are of a similar colour, but shading into a dark smoke colour at the hind margin.
The caterpillars feed at first on the grains of wheat, on the ears of which the moth deposits the eggs in June. At harvest time they remain hidden among the husks, and are often threshed out in large numbers by the blows of the flail. The cold weather soon overtakes them, and they then spin a cocoon in which to pass the winter. On the approach of spring they come out again, and feed by night on various low plants, hiding themselves among the roots by day. In March they are full grown, and change to brown chrysalides beneath the surface of the ground.
The moth flies in June, and is one of the commonest and most destructive of our Noctuæ.