Part 17

FIG. 94.—The Peacock Butterfly (Vanessa io), with pupa, and larva suspended before passing into the pupa state. ]

Among butterflies with larvæ that become suspended pupæ are the =Red Admiral= (Vanessa atalanta), the =Peacock= (Vanessa io, Fig. 94), the =Fritillaries= (Argynnis), the =Meadow Browns= (Hipparchia), etc.; and among those with girdled pupæ the =Swallow Tail= (Papilio machaon), the =Whites= (Pieris), etc.

The =Cabbage White=, or =Large White= (Pieris Brassicæ).

Butterfly: Length a little over an inch, span of wing 2½ inches. Both fore and hind wings milky white, the former black at the root, on the front edge, and the outer angle; also a black patch on the inner margin of the fore wing, passing on to the front margin of the hind wing. The female possesses, in addition, two round black patches on the middle of each fore wing. Under side of the fore wings milky white, yellow at the tip, blackish at the root; under side of the hind wings yellow, with black dots. Caterpillar (Fig. 95): As much as 1⅓ inch long; greenish, or sulphur yellow, with black dots. Head and dorsal side of last segment of the body grey with black spots. Young specimens are of a very bright green with black wartlets closely crowded together.

FIG. 95.—The Cabbage White (Pieris brassicæ) female laying her eggs; caterpillar, and pupa. ]

From the pupæ which have lived through the winter butterflies emerge in May, and lay their golden yellow eggs in small heaps on the under sides of the leaves of rape, mustard, and cress, also on charlock and such-like cruciferous weeds. The caterpillars of this first generation are hatched in fourteen days, and rarely do any harm, since they only appear in small numbers. They develop rapidly, and during the last days of June become pupæ on the branches and leaves of the plants they live on; the butterflies appear in July. Owing to their rapid development the caterpillars and pupæ of this first generation are but little exposed to the attacks of enemies (ichneumons, birds, etc.). Only a few of them die, therefore, if the weather is favourable. As a result of this, the July butterflies and the eggs laid by them are relatively numerous, so that the number of caterpillars appearing in late summer may be very large. These caterpillars, however, live almost exclusively on the various kinds of cabbage and kohl rabi, and it is this second generation which in many years is so harmful. At the beginning of August the caterpillars are ready to become pupæ, and for this purpose they seek tree stems, hedges, walls, etc. The pupæ now formed live as such through the winter. During this period, however, they are exposed to many dangers (damp, cold, sudden alternation between very low and very high temperatures; ichneumons, birds), and most of them perish, so that only a few butterflies come out the following spring, and lay but a few eggs. It is therefore obvious that the first generation of caterpillars (May, June) is much less numerous than the second generation occurring from late summer to autumn. Under exceptionally favourable conditions even a third generation may appear, since caterpillars of the second generation are able to become pupæ at the beginning of August; and these pupæ, instead of remaining as such over winter, become butterflies the same month. These, again, lay eggs from which the caterpillars of the third generation are hatched, which, however, are not always fully developed before the advent of the cold weather, and in this case perish. It is clear that, in the case of pupæ which develop into butterflies during August in about fourteen days, the unfavourable influences have either no effect (unfavourable weather) or but little (ichneumons, birds), so that the butterflies appear in flocks, which wander into other regions, since they have themselves, when larvæ, devoured the cabbage and turnip plants. In reference to the damage effected by the caterpillar, it may be observed that only the chief veins of the leaf are left, and the margins are not spared. Remedies: Collection of the little heaps of yellow eggs and the young caterpillars, which are blackish and live together in small companies; the planting of a few small hemp plants in the cabbage fields to be protected, by which the butterflies will be kept away.

The =Garden White=, or =Small White= (Pieris rapæ).

FIG. 96.—The Garden White (Pieris rapæ), male. ]

FIG. 97.—The Garden White (Pieris rapæ), female, caterpillar. ]

Butterfly (Figs. 96 and 97): Length rather less than an inch, span of wing two inches; very much like the cabbage white. Base and tip of the fore wing not of such a deep black colour; the black patch in the inner margin of the fore wing is usually absent in the female. The male, however, very often has a black patch in the upper side of the fore wing. Caterpillar: Just over an inch long. Dull green; a longitudinal yellow line on the back; also the black stigmata are connected by a yellow line. Habits as in the preceding species; the female, however, lays her yellow eggs separately, and not in heaps, and the second generation of caterpillars usually become pupæ somewhat later in the year. Collecting is more difficult than in the preceding species, since the young caterpillars live independently, and their colour makes it difficult to recognize them on the green cabbage leaves.

The =Green-veined White= (Pieris napi).

Butterfly (Fig. 98): As large or somewhat smaller than the preceding species. Wings milky white on their upper side; fore wings dusted with black on their front margin, tips, and ends of the ribs. Two spots on the middle of the fore wing in the female, one or none in the male. Under side of the hind wings yellow; under side of the veins dusted with greenish grey. Caterpillar: A little over an inch. Dull bluish-green, with minute blackish tubercles above, and whitish ones below. A yellow longitudinal line on each side connecting the black spiracles, which are bordered by reddish yellow. Very like the preceding species in the larval condition. Habits as in the preceding species, but this is less common.

FIG. 98.—The Green-veined White (Pieris napi). ]

Family: =Noctuidæ= (Owlet Moths).

Night-flying moths, of medium size and dull colour, with smooth-haired bodies. Antennæ long and thin, thread like,—comb-shaped only in the males of a few species; wings powerful, lie in a roof-like way when at rest; almost always a wing-hooklet. Caterpillars usually hairless; mostly with five pairs of pro-legs, a few with four or three pairs. The owlets pair at night; they also fly about during the day, even in bright sunshine. Flight strong and rapid, but always in fits and starts. Almost all species lay their eggs separately, and on herbs, only a few species on trees. The caterpillars are very much scattered, and the damage caused by them is never great, except in spots here and there,—on the contrary, when they increase to a great extent they spread over a wider area. Several species are harmful to agriculture.

The =Surface Caterpillars= (Species of Agrotis)

are stout caterpillars, 1⅕ to 2 inches long, with five pairs of pro-legs, and shining transparent external skin. They remain in the ground during the day, feeding above ground at night, and also in the daytime when the sky is much overcast. When touched they bend themselves into the form of a C. There are in Britain several species of surface caterpillars which have these habits, but I will only describe here, to begin with, the commonest kind:—

FIG. 99.—The Common Dart or Turnip Moth (Agrotis segetum) with Caterpillar. ]

The =Common Dart= or =Turnip Moth= (Agrotis segetum or A. clavis).—Moth (Fig. 99): Length almost ⅘ of an inch. Span of wing about 1⅘ inch. Fore wings small, ash-grey or brownish, with many dark patches and similar markings. Hind wings in the male, bright grey to snowy white; in the female, brownish grey. Caterpillar (Fig. 99): Up to two inches, earthy grey, occasionally somewhat greenish. Head and prothorax darker. The time taken by the caterpillars to complete their development differs according to the plants attacked, and it is therefore easy to understand why the moths should be seen flying about from the first half of May right on into the autumn, without having recourse to the improbable hypothesis of two successive generations. The eggs are consequently laid at very different times, and are always deposited singly in the soil in the neighbourhood of plant roots, or else in the low-lying leaves and stems of various herbs. The caterpillars hatched from these are destructive earlier or later, according to the time of egg-laying. Most specimens are half grown in winter; these continue their destructive work the following spring. In autumn they attack the roots of winter grain (rye and wheat), rape, and species of cabbage; they also bore readily into turnips and potatoes. In spring, after the winter rest, they continue to attack the roots of winter grain, winter rape, etc., or fleshy underground parts (turnips, potatoes) developed in the interim, or the roots of summer plants (summer grain, buckwheat, summer rape, vegetables, etc.). On clear days the caterpillars always remain hidden in the soil; and those which have bored into juicy underground parts of plants (turnips, carrots), do not leave their abode during the day, but the others, both during the night and on cloudy days, come above ground to attack the leaves and stems of young plants. In exceptional cases the caterpillar is mature by the beginning of winter, in which case it hybernates in the soil as a brown pupa. The moths escaping from such pupæ naturally appear earlier than others. As a rule, the caterpillars do most damage to the winter crop in autumn, wandering about a great deal; in many cases they gnaw through the main root, thus quickly killing the plant attacked, from which they proceed to another. Remedies: When the caterpillars have done much damage in late summer, it is recommended to leave the field alone till October, then to plough it up and sow the winter grain. By putting off the seed-time in this way, the caterpillars will have lost their activity when the corn germinates, and the winter crop will thus escape them. Besides this, the preceding ploughing will bring many caterpillars to the surface, where they will become the prey of birds, or, if not, can be collected. Warm soils, especially those manured with horse dung, are most infested by the caterpillars; and the use of warm kinds of manure should, therefore, be avoided in regions which have much to fear from these insects. Where everything has been destroyed, a thorough ploughing is desirable. Swine may also be driven in during autumn, and will grub up and devour the caterpillars. In this case, sowing will take place the following spring.

Other Surface Caterpillars, which have pretty much the same habits as the preceding, are those of the =Heart and Dart Moth= (Agrotis exclamationis), the =Wheat Moth= (A. tritici), and the =Thick-bodied Surface Caterpillar= (A. ravida or A. crassa).

The =Cabbage Moth= (Mamestra brassicæ).

Moth (Fig. 100); about ¹¹⁄₁₂ of an inch long, span of wing 1⅗ inch. Fore wings shining brown, with yellowish and black marbling; each patch having a dark outline; a yellowish zigzag line on the outer margin. Hind wings shining yellowish-grey brown. A strongly developed crest in the middle line of the thorax. Caterpillar (Fig. 100): 1⅗ inches, cylindrical. Bright or dark green, brownish green, or greenish brown. On the back a dark longitudinal stripe, divided into two halves by a narrow white longitudinal line. A whitish line running along each side; between this and the dorsal line a dark transverse streak on each segment. The brown pupa (Fig. 100) remains in the soil during the winter, and is not invested in a cocoon. The moth appears in May; during the day it rests on windows, in barns, etc. The greenish yellow eggs are laid separately on the leaves of cabbages (sometimes also on lettuces and turnips). The caterpillars, which appear in fourteen days, creep about actively between the leaves. Within a month they are full-grown, and become pupæ in the soil. At the end of July and in August the summer generation of moths appears. From the eggs laid by these are hatched a second generation of caterpillars, which are always much more numerous than those of the first. From August to October they are found in all kinds of cabbage, especially compactly headed kinds and cauliflower. At first they eat holes in the leaves, leaving, however, the chief veins and usually the edges. Later on they eat right on into the heart of the cabbage. They fill their burrows with excrement, and the attacked plants begin to rot internally. The full-grown caterpillars creep out and become pupa in the soil. Remedy: Collecting the caterpillars while they are still on the outer leaves.

FIG. 100.—The Cabbage Moth (Mamestra brassicæ), with caterpillar and pupa. ]

The =Vegetable= or =Lettuce Moth= (Mamestra oleracea).

Moth: ⅗ of an inch long; span of wings about 1⅖ of an inch. Fore wings dark rusty brown, darker on the nerves, dusted with white. Hind wings reddish white. Head and thorax like the fore wings; abdomen like the hind wings. Caterpillar: Up to 1⅗ inch; dirty greenish grey, or olive green, irregularly bestrewn with dirty white dots. The caterpillars feed on cabbages, lettuce, asparagus, and other vegetables. Those of the first generation (June and July) hollow out lettuce stalks before the head begins to be formed; those of the second generation (August and September) feed on cabbage or asparagus leaves. The first generation of moths appear in May, the second in the first half of August.

The =Pea Moth= (Mamestra pisi).

Moth: About ⅖ of an inch long; span of wings about 1⅖ of an inch. Fore wings bright reddish brown with bluish-grey markings, and a yellowish longitudinal streak. Hind wings reddish grey. Caterpillar: 1⅘ of an inch; cylindrical; slender. Back dark greenish or brown red; closely and tolerably regularly veined with dark lines, and with two sulphur yellow longitudinal streaks on the back and one on each side. Head, belly, and feet flesh red. If the caterpillar is touched it moves the front part of its body about here and there, and then lets itself fall down. The moths appear in May and June; the caterpillars are found from July to September on peas, vetches, beans, clover, lupins, sorrel, orach, heath, willow, birch, and yet other plants. Seldom very destructive.

The =Grass-root Moth= (Hadena monoglypha, or H. polyodon).