The reason a fly swatter is an efficient tool for killing flies while the human hand is not is as follows: a fly’s tactile sense is controlled by numerous sensory hairs covering its entire body. These hairs are especially sensitive to air pressure. The movement of a hand or any other solid object creates fluctuations of air and warns the fly well in advance of the blow. The fly swatter, however, has many holes arranged along its surface, so that it displaces little air as it bears down on its victim. Thus the fly is caught unaware.