Turnip Fly, a name given to several insects of different orders, but especially to the small chrysomelian beetles of the genus haltica (Illig.), which attack the turnip in its various parts and stages of growth. In the genus haltica (Gr. denude, skilled in leaping) the body is very convex above, oval, with short thorax and wide head; antennse slender; hind thighs very thick and formed for leaping; surface of the body generally smooth and shining, and often prettily colored; claws notched and hooked, enabling them to keep firm hold of the leaves of plants on which they feed, especially the cruciferous vegetables, to which they are often very injurious. They are all very small, the largest not more than two lines long and one line wide; most are shining green, tinged with brown or yellowish. The turnip fly of England is the H. nemorum (Illig.); it devours the seed leaves of the turnip as they appear above the ground, continuing its ravages all summer; in winter it conceals itself in some dry and sheltered place, laying its eggs in spring on the leaves; the larvse eat the soft pulpy substance, making little galleries in which they undergo their changes, and in this way are as injurious as the full-grown beetles; they are slender grubs, tapering at each end, with six legs, and become perfect insects in a few weeks, a constant succession occurring through the summer.

The loss to the turnip crop from their ravages is sometimes very large. (See Turnip.) The H. striolata (Fabr.), the wavystriped flea beetle of the United States, much resembles the preceding; it is less than 1/10 of an inch long, shining black, with a broad, wavy, buff stripe on each wing cover, and the knees and feet reddish yellow; it is abundant on the seed leaves of the turnip and other plants early in May, in some seasons threatening to be almost as injurious as the European insect. - Among the lepidoptera, the pontia oleracea (Harris), potherb or white butterfly, is often called turnip fly. The wings are white or yellowish, dusky near the body; back black, and antennae blackish with narrow white rings; the expanse of wings about 2 in. Toward the beginning of June it may be seen fluttering over turnip and cabbage beds for the purpose of attaching three or four of its eggs to the under side of the leaves; the eggs are yellowish, pear-shaped, ribbed longitudinally, and 1/15 of an inch long; they are hatched in about 10 days, attain their full size of 1¼ in. in three weeks, when they are pale green, and eat irregular holes in any part of the leaf; they pass a chrysalis state of 11 days, suspended by silken threads attached to the hind feet and fore part of the body in some protected place.

They are again abundant toward the beginning of August, laying eggs for a second brood, the chrysalids from which survive the winter, coming out perfect insects in May or June; the chrysalis is four fifths of an inch long. The larvae are eaten by titmice and other insectivorous birds; the chrysalids can be collected on boards placed for them near the ground, and the butterflies are easily caught in bag nets, as they fly low and lazily. This species is rarely found S. of the latitude of New Hampshire. - Some dipterous insects, as the flower flies (anthomyiadoe), in the larva state infest the roots of turnips, etc, eating also the pulpy parts of the leaves and stems.

English Turnip Ply (Haltica nemorum).

English Turnip Ply (Haltica nemorum).

White Butterfly (Pontia oleracea).

White Butterfly (Pontia oleracea).