Page:The Zoologist, 1st series, vol 1 (1843).djvu/152

124 sown earlier, had grown too large to be so easily destroyed: 2ndly, On account of the property of the leaves to retain water longer than those of any other turnip. Thousands of these little insects might be observed sitting on the under side of every leaf, which they did not eat, but extracted the moisture from it in such a manner, that at the end of three or four days the turnip was completely killed, and could be crumbled between the finger and thumb, like scorched leaves. Between five and six hundred acres of turnips were totally destroyed in this way in the neighbourhood of Alnwick and Wooler, particularly about Millfield-plain and Flodden-field, though in the southern parts of the county, and on the Scotch side of the Tweed, there were none to be seen, or at least so few as not to be noticed. They were also sometimes found on the wheat and oats, and in one instance a quantity of wheat was entirely spoiled from having been bound up into sheaves with a great number of Aphides upon it. On the sheaves being opened again after two or three days, they appeared as if glued together, and had a very offensive smell, and the wheat was of course entirely useless. The Aphides were never found upon ripe oats, but were more numerous on the unripe than on any other kind of corn.

Various kinds of insects used to feed on these Aphides:—the red and black ants, Ichneumon flies, the larva of the large red lady-bird, and the caterpillar of a fly whose name I do not know. These caterpillars used to seize the Aphides and suck their juices from them: this was a very curious operation; when the insect had seized his prey, he raised his head in the air, and continued in that position until there was nothing left but the skin of the Aphis, which it got rid of by (as it were) wiping its mouth on the turnip-leaf. In this manner it would eat from fifteen to twenty at a time, and then remain inactive for half an hour, and then again feed, one caterpillar would thus destroy about a hundred in a day. The colour of the caterpillar was a transparent green, barred towards the tail with reddish brown and yellow, in length about half an inch. The chrysalis was reddish brown, always fixed on the underside of a turnip-leaf. The fly was about half an inch long, head large, and, together with the thorax, reddish brown; the wings as long as the body, rounded and transparent: the body darker brown approaching to black, barred with bright yellow like a wasp. The caterpillar was about ten days old before it became a chrysalis, and remained in that state other ten: the flies lived only three or four days, but were very quick and active, continually hovering over the turnips in great numbers, and appearing to settle on them very seldom, and then only for an instant. I kept a great number of