Note 317 — LETTER VI.

De Geer, ii. 440. In the summer of 1826 when at Brussels, I observed that delicious vegetable of the cabbage tribe so largely cultivated there under the name of Jets de choux, and which in England we call Brussels sprouts, to be materially injured in the later stages of its growth by the attacks of the turnip-flea, and other little beetles of the same genus (Haltica), which were so numerous and so universally prevalent, that I scarcely ever examined a full-grown plant from which a vast number might not have been collected. Some plants were almost black with them, the species most abundant being of a dark æneous tinge. They had not merely eroded the cuticle in various parts, so as to give the leaves a brown blistered appearance, but had also eaten them into large holes, at the margin of which I often saw them in the act of gnawing; and the stunted and unhealthy appearance of the plants sufficiently indicated the injurious effect of this interruption of the proper office of the sap. What was particularly remarkable, considering the locomotive powers of these insects, was that the young turnips, sown in August after the wheat and rye, close to acres of Brussels sprouts, (which all round Brussels are planted in the open fields among other crops,) infested by myriads of these insects, were not more eaten by them than they usually are in England, and produced good average crops. It would seem, agreeably to a fact already mentioned, (see Vol. I. 4th Edit. p. 389,) that they prefer the taste of leaves to which they have been accustomed, to younger plants of the same natural family; and hence perhaps the previous sowing of a crop of cabbage-plants in the corner of a field meant for turnips, might allure and keep there the great bulk of these insects present in the vicinity, until the turnips were out of danger.