FIG. 310. LARGE WHITE CABBAGE BUTTERFLY.
FIG. 311. SMALL WHITE CABBAGE BUTTERFLY AND CATERPILLAR.
The perfect male insect has the body black and wings white on the upper side, except the tips of the fore-wings, which are black and crescent-shaped; and on the upper edge of the hinder wings there is a black spot. On the under side, the fore wings are white with yellow tips, and two black patches on each; the hind wings are yellow, with small black markings. The antennæ are alternately black and yellow, with the club black above and yellow beneath. The female (see Fig. 310) differs from the male in having two large black spots on each of the fore or upper wings, and a spot on the inner margin.
The Small White (Pieris rapæ, see Fig. 311) has two broods in the year, the first batch about April, and the second in July. The eggs are always placed on the upper side of the leaf, and are hatched in from ten to thirteen days, the caterpillars becoming full grown in about three weeks after emerging. The colour of the caterpillar is dark green, with a fine line of yellow, and a row of yellow spots down the sides. The chrysalis is attached by the tail and a band of silk to the place selected by the caterpillar, and varies greatly in colour, although generally it is of a whitish-brown.
Cabbage Moth (Mamestra brassicæ). Newman, in his "British Moths," thus describes the Cabbage Moth: "The antennæ are rather long and slender, and scarcely ciliated in either sex; the fore-wings are dark, smoky, grey brown, mottled and marbled with confused markings, both darker and paler; the orbicular spot is inconspicuous, but decidedly to be traced; the reniform stigma is delicately outlined with white or whitish-grey, and has a pale anterior disc, in which the same pale grey colour predominates; the hind wings are dark, smoky brown with rather pale base, and rather darker crescentic discoidal spot and wing-rays; the head, thorax, and body have the same colour as the fore and hind wings." The eggs are laid on Cabbages, or similar plants, and are hatched in a few days. The caterpillars are very voracious, feeding by day and night, and, what is worse, they spoil with their excrement, in the case of Cabbages, more than they eat. They are of a dark colour, with a kind of marbling, more or less distinct, on the back, the effect being produced by a triangular mark containing two white dots on each of their segments. On being disturbed, they roll themselves into a tight ring, and so remain until they suppose that danger is over. They descend into the earth for change to smooth red-brown chrysalids, and remain there till the following spring. If the chrysalids were collected and destroyed during the autumn and winter digging, much injury would be obviated through the succeeding spring and summer.
The destruction of these pests is a very troublesome matter, as the grubs of the last-named kind bore into the heart of the cabbage. Hand-picking is the only sure method. Anything emitting a distasteful odour will also keep them at bay. Miss Ormerod recommends throwing gas-lime over the plants, but it must be previously weakened by a few months' exposure. The following remedy may also be recommended:
Paraffin, or Coal Oil. Mix one ounce of oil with a gallon of soapsuds, and water the plants with the mixture before the caterpillars appear. If any have appeared, an application at the rate of two ounces to the gallon will generally clear them off. Of course, this operation must not be performed less than a month previous to cutting the cabbages, on account of the smell. Soapsuds alone will also clear caterpillars from most smooth-leaved subjects if frequently applied.
CABBAGE FLY (Anthomyia brassicæ). Among the injurious insects which infest Cabbages, none commit greater havoc to both stem and root, than the maggots of the Cabbage Fly. "They are whitish, cylindrical, and legless, tapering to the head, and blunt at the tail, which has short teeth on the lower margin, and two brown tubercles in the middle. When full grown, they are about ⅓in. long. They then leave the plants, and turn, in the earth, to pupæ, with a few black spots at the head, and short teeth at the tail, inside which the flies form, and emerge in about a fortnight or three weeks. The fly is of an ashen-grey colour, and smaller than the Onion Fly, which it much resembles. The male is of a darker grey, and has a short black stripe along the back between the wings, with a curved one on each side of it, and one black stripe along the abdomen" (Ormerod). The presence of these maggots may be easily detected by the flagging and change of colour of the leaves. The infested plants should be immediately removed and destroyed. The following remedy will be found beneficial: