THE TRUE BUGS 



129 



FIG. 177. Aphis 



eggs on twig. 



(Natural size) 



(After Weed) 



called honey-dew, and are constantly attended by ants, which 

 eagerly devour it. In the case of several species the ants care for 

 them almost as if they were their domestic animals, 

 and very commonly ants are responsible for carrying 

 the aphides from one plant to another as the food 

 supply becomes exhausted, as in the case of the melon 

 aphis and the strawberry root-louse. Among the more 

 common species are the common green apple aphis 

 (Aphis pomi), the cabbage aphis, the pea aphis, which 

 often destroys entire crops of garden peas in the At- 

 lantic states, the green bug ( Toxoptera graminum), 

 which has recently been so 

 injurious to grain crops in 

 the southwest, the melon 

 aphis, the rose aphis, the 

 chrysanthemum aphis, 

 and a host of others. The 

 foliage of almost every 

 plant is attacked by one 

 or more species, and many of the most in- 

 jurious attack the roots, as the corn root- 

 aphis (Aphis maidi-radicis\ which is one 

 of the most serious corn pests in the Miss- 

 issippi Valley. The grape phylloxera, an 

 American species attacking the roots of 

 the grape, was imported into Europe and 

 soon became the worst enemy of the vine 

 in France, where it has caused the loss 

 of millions of dollars. Several species 

 exude a cottony mass of wax over the 

 body, so that they appear like a mold. 

 Among these the woolly apple aphis is 

 often seen on the leaves and on wounds 

 and scars on the bark of apple trees, and 

 a similar species covers the twigs of alder 

 as if they were wound with cotton. 



The scale insects (Coccidae). Some of the worst insect pests of 

 the fruit orchard belong to the scale insects, which are so peculiar 



FIG. 178. Tip of dock stem 

 covered with black aphides 



