In the U. K. most adults are medium sized with fat bodies, and often brown coloured. Worldwide the adults are usually brown or grey, but some have brilliantly coloured underwings which they flash when disturbed. All adults are nocturnal, and are often called the Owlets. Most have powerful flight, and rest with their wings held tent-like over their body - see the Silver Y on the right. Wingspan ranges from 30 - 50 mm.
Adults have a pair of hearing organs (tympana), one of each side of the thorax. The moths themselves do not make any noise, but the tympana allow them to detect the high-pitched sounds made by echo-locating bats, which are a major predator.
The caterpillars tend to be hairless, below is the typical Noctuidae caterpillar body.
Right and below right is the Silver Y moth, Autographa gamma. So-called because of the white y mark clearly seen on its front wings. It is abundant in the UK and Europe, and flies both day and night. Though it is abundant it cannot overwinter in the UK, and is most commonly seen flying in the autumn. It migrates to the U. K. from North Africa and southern Europe. Its wingspan is 32 - 43 mm and forewing length 13 - 21 mm.
Eggs are laid in May and August, however the the eggs laid in August do not survive to breed as adults. The eggs are pale and shiny and vary in colour from green to dark olive.
The caterpillar has only two pairs of prolegs and feeds on almost any kind of plant, but can be a pest species on cabbage and pea plants.