Page:Popular Science Monthly Volume 16.djvu/806

 long, slender tube for pumping the nectar of flowers. This "proboscis" is frequently much longer than the insect's body, and when not in use is beautifully coiled under the head. The hummingbird has a long, slender beak for the same purpose, which in some species is curved to fit certain flowers, it is said. Bees and flies lap their food, the former with a hairy tongue, the latter with a proboscis knobbed at the end. The sucker of the leech is furnished with three little saws for cutting the skin of its prey in order to draw its blood. A barbed tube is used by the louse; while the irrepressible mosquito is provided with a whole set of surgical instruments. Its proboscis, which seems so simple to the unaided eye, is found to be a "flexible sheath inclosing six distinct pieces, two of which are cutting-blades or lancets, two notched like a saw with reverted teeth, a tubular canal, and the central one an excessively acute point, which is also tubular."



It is interesting to know how the insect uses so many instruments, as we have all had the pleasure of being the subjects of her surgical skill (for only the female is admitted to the practice of bloodletting). "When the attack is made, the gnat (or mosquito) brings the tip of the organ within its sheath to press upon the skin into which it presently enters, the sheath remaining without and bending into an angle as the lancets descend. When the weapon has penetrated to its base—a distance of one sixth of an inch or more—the lancets move laterally and thus cut the flesh on either side, promoting the flow of blood from the superficial vessels; at the same moment a highly irritative fluid is poured into the wound, which has the effect of diluting the blood and thus rendering it more capable of flowing up the slender central tube into the throat of the insect."

Many aquatic animals, especially the low, fixed forms, depend for subsistence upon the minute organic particles floating in the water. But if the animal can not move in search of food it must have some means of bringing the food to itself. This is frequently accomplished by vibrating hair-like appendages, called cilia, which produce currents