Noctua
(Night Moths). A name applied with a considerable diversity of comprehensiveness in respect to the number of insects included under it, though, even in the widest acceptance, the species are all heavy in body, with somewhat narrow front wings, dull coloured, but variegated with spots and cross bands. Used originally to denote any member of the great group now called Noctuina, it became restricted to the family Noctuidae, and finally to the genus Noctua. A brief account of the family Noctuidae is here given. The distinctive characters are not easily put into words, yet the general aspect is somewhat easily recognised in the family. The front wings are narrow and laid flat, and so overlap as to render the whole insect narrow when at rest. In most of the species, the spread of wings averages about 1 1/2in., varying from 1in. to 2 1/4in. The larvae are usually cylindrical, thick, and smooth, and hide during the day either below ground or in and below the plants on which they feed at night: they are usually dull in colour of markings. The pupae are protected in earthen cocoons underground. The family includes four British genera, viz.: Rusina with one species, which has the fore wings brown, with three dark cross lines, and the hind wings dark grey, with darker fringes; Triphaena (the Yellow Under-wings), from 1 1/4in. to 2 1/4in. in spread of wing, easily known by the hind wings being yellow or orange, with a black band along the rear margin; Agrotis (the Dart Moths), and Noctua, both of which latter have grey hind wings, and vary from 1in. to 2in. in spread of wings; the chief differences between them resting in the narrower fore wings, and, in Agrotis, different arrangements in markings of the fore wings. Agrotis numbers twenty-three British species, Noctua twenty, and Triphaena six. The larvae of almost all these genera devour herbaceous plants or Willows; and many of them can thrive on a large variety of plants. Some attack the roots, others the leaves and the young stems, of many of our cultivated potherbs; and a considerable proportion may be included among the most hurtful of garden pests. Indeed, this family probably contains the Moths most hostile to gardeners. Noctua is, perhaps, the least injurious of the three genera, since few of the larvae in it are in the habit of feeding largely on garden produce. Triphaena, though with fewer species, is probably more destructive; but pre-eminent in this respect is Agrotis. In this genus, many of the species live habitually on Turnip roots (see Turnip Moth), on Cabbages, and on almost all other vegetables grown for food. The most injurious kinds may be specified as the Turnip Moth (A. segetum), the Heart and Dart (A. exclamationis)--like the last, very destructive to Turnip roots in winter, though omnivorous when pressed by hunger--the Garden Dart (A. nigricans), and the White-line Dart (A. Tritici); though several of the remaining species are also harmful at times. To attempt to describe the above species individually, would far exceed the space available here.
Amongst the best methods for getting rid of the caterpillars are to lay soot or gas-lime around the stems of the plants, so as to prevent access to them; or to manure with guano, and earth-up the plants, to stimulate repair of injuries caused by the insects. If only a few choice plants are attacked, it is advisable to remove the soil from the upper part of the root, and to pick out the larvae; or to examine the plants with a lantern at night, and to pick off such as are visible. Those that live in the hearts of the plants cannot be removed without the destruction of the parts in which they lie. In the protection of Turnips, and other field crops, rooks and partridges afford the best aid, though starlings and other birds also eat not a few larvae.