"There is, boys, something well worth attention; did you ever see a mask?"
"Do you mean, Uncle Philip, a face made of pasteboard, very frightful commonly, which you can wear over your own face?"
"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."
Mask of the Dragon-fly, shut and open.