"That is a mask, boys; but so is any thing which is made to wear over the face, and hide it. Now this little insect has a mask, not made like a man's face, but which completely hides its mouth, and it is exceedingly curious." "How is it made, Uncle Philip?" "Why, boys, I am not sure that I can tell you, so that you will understand me; but I will try. Suppose your under-lip was horn, instead of being flesh; and suppose it hung straight down until it reached the bottom of your chin, so as to cover the whole of it, and that at the bottom there was a large three-sided plate which was hollowed out, and fastened by a joint or hinge to the bottom of your long lip, so that it could turn up on the hinge and cover your face as high up as your nose, and hide your long lip and your mouth and part of your cheeks: suppose, too, that at the upper end of this long face-cover there were two other pieces, so broad that they would cover all your nose and your temples, and could open sidewise like jaws, and show your nose and mouth, so that when they were opened they would appear like the blinders to a horse's bridle; and then suppose that these jaws, upon their inner edges, were cut into a great many sharp teeth, which fitted into each other, and you will have some notion of this curious mask. Do you think you understand me?" "Why, pretty well, Uncle Philip, we think." "Well, boys, here are some pictures, and with their help I hope what I have been saying will be plain enough. In one picture the mask is shut; and in the other, one of the jaws, like a blinder to a bridle, is open. While the insect is at rest, it keeps the mask over its face; when it wishes to use it, it unfolds it, and catches its food, and holds it to its mouth. A gentleman once saw one of them holding and eating a large tadpole." [Illustration: Mask of the Dragon-fly, shut and open.] "Uncle Philip, this mask is any thing but handsome." "Very true; but you know we agreed when we were talking about the bats to look at animals even if they were not handsome. And there is your poor little ugly insect that you thought it right to kill, the spider; did you know that the spider was a sailor, too?" "No, indeed, Uncle Philip! Pray tell us of it, will you?" "Yes; but wait a little, until we bring the boat's head right, for we are near the landing-place. So--now, boys, I am ready. There is a very large spider, about which not much is yet known, which actually builds a _raft_, for the purpose of getting its food more easily. You may see it sailing about upon the water, on a ball of weeds about three inches across, which is held together probably by small silk cords spun from itself; and the moment it sees an insect drowning, it leaves the raft, gets the insect, and then returns to eat it at leisure. If you frighten it, or it thinks danger is near, in an instant it is under the raft out of sight." "Ah, this is a cunning spider, Uncle Philip."