A dozen little girls at the party made up their minds promptly that after this evening they, at least, would make war on flies.
"And aren't flies of any use?" asked Betty.
"There is one little fly, Mrs. Tachina-Fly, who is of some use. She is a cousin of the house-fly. She is of use because she chooses a queer place to lay her eggs--on the back of a young caterpillar. After these caterpillars grow and shut themselves up into a cocoon to change into a butterfly the little fly eggs hatch out into maggots. Of course they are hungry--all babies are; and finding the nice, fat caterpillar in the round house, like dutiful babies they eat what is set before them until the fat, tender caterpillar is eaten up. After they are satisfied they lie still in their brown skins and change into grown-up tachina-flies, and at last out come a lot of busy, _buzzing_, bothersome flies. It is rather hard on the caterpillar. But when we think what harmful, greedy things most caterpillars are, perhaps it is good that there are tachina-flies to eat them. Is it time for supper yet?"
"No, not yet," replied Mrs. Reece. "Do tell the children something about mosquitoes."
"If I had to choose between Mr. and Mrs. Mosquito, I should take Mr. Mosquito, for he neither bites nor buzzes, but attends strictly to his own business. Perhaps he thinks Mrs. Mosquito's voice pretty. Perhaps he likes to hear about her adventures. But most people do not, for they think Mrs. Mosquito a busybody, always going where she is not wished, always breaking up conversations, and always coming back after she has been plainly told that she is not wanted. Yet her singing is music in the ears of her husband. Perhaps if we had long, slender antennæ, all covered with hairs, like his, we, too, might like her song. When she sings these hairs begin to tremble, to vibrate, and a little nerve in the antennæ changes this trembling to sound.
"In every way Mr. Mosquito seems a more pleasant body. He eats very little, and contents himself with nectar. But she, knowing that excitement makes the blood flow faster, and being a hearty eater, begins her song gently at first, then louder and louder, nearer and nearer. Finally, with her long, slender, sharp stylets, she makes a hole in your cheek or your arm, pushes in her sucking-beak, and pumps up the blood. And there she sucks and sucks until her stomach is full or she is brushed off or killed."