Now in such places every one knows that there are quantities of midges, and also that these insects are always exceedingly thirsty. They prefer blood, it is true, but when they see these bright yellowish leaves they naturally go to them. When, however, the midge touches the leaf, the sticky liquid clings to its wings and legs, and it cannot escape.
So far this does not differ from the Fly Catchers mentioned above, but another very curious action then begins. If the midge or fly is near the margin of the leaf, the edge of the latter begins to curl or roll inwards over it. It does so very slowly, and may not finish rolling over the insect for some hours. Whilst this is going on acids and "gastric juice," or ferments which act in the same way, are being poured over the body of the midge, which is finally completely digested. Next day, having finished the midge, the leaf majestically unrolls itself again and waits for another.
The juice contains rennet, and is used by the Lapps in making a horrible delicacy called Tätmiölk. It has also been used by the Swiss shepherds for at least two hundred years, to cure sores on cows' udders.
The other British plant is the Sundew (Drosera). Every one who has been on peat-mosses and moors probably knows its little reddish rosettes of small rounded or spoon-shaped leaves lying on bare peat or wet mossy ground. Each leaf seems to be covered by hundreds of glittering little dewdrops (whence the name).
The hairs or tentacles which cover the leaf secrete this glistening, sticky fluid. There must be about two hundred of them on a single leaf.
An insect flying about near the Sundew is sure to be attracted by the conspicuous glittering, reddish leaves, and probably alights upon it. Then it finds itself caught and begins to struggle, but this simply brings it against more tentacles.
Now happens the most wonderful part of the whole performance. All the neighbouring tentacles, although they have not been touched, bend over towards the struggling insect and pin it down in the middle of the leaf. They do not bend over very quickly. In two or three minutes they will bend over towards it through an angle of forty-five degrees, and it takes them ten minutes to bend over ninety degrees.
There is something rather horrible in the sight of a large insect struggling with these slow, remorseless, well-aimed tentacles; most people free the insect unless, at least, it happens to be a midge. The point which is so difficult to understand is to know how those untouched tentacles know that the insect is there and exactly where it is. There is no doubt that they do know, for they behave exactly as if they were the arms of a spider.
If you put two insects on either side of the middle of the leaf, half the tentacles will pin down one and the other half will deal with the other insect.
At the same time acids and ferments are poured out which digest the insect. It takes about two days for a leaf to finish off an insect, and then the tentacles again unclose.