Paris green and blue vitriol, both very poisonous, are often used on grape vines before the grapes are formed, and very gaudy vines they are for a little while after this bright poison has been sprayed upon them. Although insects are so very interesting, we have to protect ourselves against many species in order to live. Yes, John, it is oftentimes merely a question which shall profit by the crops we plant, the insects or ourselves. Sometimes the insects win, sometimes we win, but it is a closely contested warfare all the time. We plough the land and take care of it, we plant the seeds and keep out the weeds. Then, when we have a fine crop growing, along come certain destructive insects, feeling very happy, no doubt, to have found such a feast. Now the fight begins. They attack the crop, we attack them. We spray them with poisons, burn up their eggs, do everything we know how to get rid of them. Wise men have spent many years of close study finding out the habits of the insects destructive to grains and fruits, in order to be able to destroy them. Although many of the plant hoppers are such nuisances to us, there is one family of hoppers that is seldom a nuisance. THE COMICAL TREE HOPPERS Do you know the tree hoppers,--absurd little jokers that they are? Oh, yes, they are hard and three cornered, like animated beechnuts, as somebody has said. Yes, some of them have humps on their backs and some have horns. [Illustration] John says he once made a collection of tree hoppers and put them in a box with a reading glass over the top, and showed them to his friends to make them laugh. May says she saw them, and they reminded her of Brownies. Would it not be fun to have a tree hopper Brownie book! The tree hoppers jump about on the bushes and eat the juices of the plants, but there are not usually enough of them to do damage. They seldom come in swarms like some of the leaf hoppers, though sometimes they do. THE JUMPING PLANT LICE The jumping plant lice are nearly related to the tree hoppers, but they do not look at all like them. Under the magnifying glass they look like tiny cicadas. See, here is a picture of one enlarged. [Illustration] Their natural size is no larger than a plant louse. Have you not often seen them clustered close together on the young twigs of pear trees--tiny, light-colored things that jumped in all directions when you touched the twig? The name of the plant louse that infests pear trees is the pear-tree psylla. It is very destructive to pear trees, sucking out the juices of the young shoots. The pear trees can be saved by spraying them with kerosene emulsion as soon as the young leaves have opened in the spring. THE APHIDS Now, let us go in search of the aphids, or aphides, as they are also called. We shall not have to search far. [Illustration] In a very dry season we generally need not search at all. All we need do is to examine the nearest weed to find plenty of aphides.