Let us now go on to another interesting insect of the order of which we are treating, the Aphrophora, without being frightened by its disagreeable name, for there are many other names we may give it if we choose among those by which it is popularly known. In the months of June and July one sees on nearly every tree, and on plants of the most different kinds, a sort of white froth, composed of air bubbles, deposited on the leaves and branches. It is produced by an insect which the peasants in France call _Crachat de Coucou_, or _Ecume printanière_ (spring froth), and which is called in England, Cuckoo's spittle. De Geer carefully studied the metamorphoses of this insect. The Aphrophora (from [Greek: aphros], foam, and [Greek: pherô], I bear or carry) is lodged in the froth of which we have just been speaking. It lives in it, only leaving it when it has its wings. De Geer wondered why this insect confines itself during the whole of its life in liquid, and concludes that the froth has the effect of protecting the insect from the burning heat of the sun. This covering seems also to protect it from the attacks of carnivorous insects and spiders. On the other hand, its skin is without doubt so constituted that it would perspire too freely if it were exposed to the air, and the insect would very soon die dried up. Whatever explanation may be given of the necessity for this semi-aërial, semi-liquid medium, it is easy to verify the fact that the larva of the Aphrophora cannot live long out of its frothy envelope. If withdrawn from it, the volume of its body diminishes perceptibly, and the poor animal dies, like a fish taken out of its natural element. The insects which live in this froth are six-legged grubs (Fig. 84), which, when the froth is cleared from them, walk quickly enough on the stalks and leaves of plants. They are green, with the belly yellow. [Illustration: Fig. 84.--Larva of the Aphrophora (_Aphrophora spumaria_).] De Geer wished to know how they produced this singular froth, and found out in the following manner:--He took one of them out of its frothy dwelling, wiped it dry with a camel's-hair pencil, and placed it on a young stalk, recently cut from the honeysuckle, which he put into water in a glass, in order to preserve its freshness, and this is what he observed:--