116 THE INSECT WOKLD. 



its body diminishes perceptibly, and tbe 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. 



De Geer wished to know how they produced this 

 singular froth, and found out in the following man- 

 ner : 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 honey- 

 suckle, which he put into water in a glass, in order 

 to preserve its freshness, and this is what he observed : 



" It begins," says the Swedish naturalist, "by fixing itself on a 

 certain part of the stalk, in which it inserts the end of its trunk, 

 and remains thus for a long time in the same attitude, occupied 

 in sucking and filling itself with the sap. Having then with- 

 drawn its trunk, it remains there, or else places itself on a leaf, 

 where, after different reiterated movements of its abdomen, which 

 it raises or lowers and turns on all sides, one may see coming out 

 of the hinder part of its body a little ball of liquid, which it causes 

 to slip along, bending it under its body. Beginning again the 

 same movements, it is not long in producing a second ball of 

 liquid, filled with air like the first, which it places side by side 

 with, and close to, the preceding one, and continues the same 

 operation as long as there remains any sap in its body. It is 

 very soon covered with a number of small balls, which, coming 

 out of its body one after the other, tend towards the front part, 

 aided in this by the movement of the abdomen. It is all these 

 balls collected together which form a white and extremely fine 

 froth, whose viscosity keeps the air shut up in the globules, and 

 prevents its froth from easily evaporating. If the sap which the 

 nympha has drawn from the plant is exhausted before it feels itself 

 sufficiently covered with froth, it begins afresh to suck, until it 

 has got a new and sufficient quantity of froth, which it takes care 

 to add to its first stock/'* 



* " Memoires pour servir a 1'Histoire des Insectes," tome iii. 



