382 TRANSFORMATIONS OF INSECTS. 



and the sudden appearance of thousands of these insects upon 

 different plants. Fortunately they have a crowd of enemies, other- 

 wise they would do a vast amount of harm to vegetation. They 

 are found on almost every kind of plant, and upwards of three 

 hundred species have been described. The hop Aphis sometimes 

 nearly ruins the crop, and the rose Aphis, and that which is 

 found on the scented geranium also do much mischief. The 



COCHINEAL INSECT. (INIagnifiecl.) 



larvae of the CoccinellcE, or lady birds, and several IcJinaivwns, 

 devour and kill great numbers. 



The engraving on page 380 shows two immature females and 

 a male which has wings. 



The mischief done by these insects is produced by their 

 tapping the delicate tissues of the plants with their suckers, and 

 by their extracting the richest sap. They congregate in groups 

 on the stems and leaves, but in the autumn the last generations 

 emigrate from plant to plant. 



Some of the Aphides which belong to the genus Lachinis do a 

 great deal of harm to apple trees ; they are well known from the 



