902 Rural School Leaflet 



haps the winged Hoe are produced for the purpose of spreading the aphids 

 and of finding new, fresh food so that the race will not die and be lost 

 altogether. Observations seem to show that whenever a plant becomes very- 

 much crowded or begins to wither and die so that the lice have difficulty 

 in obtaining food, individuals with wings are promptly produced, although 

 all of the lice on the plant up to that time were absolutely wingless and 

 incapable of flight. The winged ones, of course, can fly to other fresh 

 plants, start new colonies, and thus preserve the species although the 

 wingless ones left behind on the old plant all perish from starvation. 



Injury to the plant. — The cabbage aphis, like all other aphids, has a 

 tiny beak, or proboscis, with which it pierces the leaves of the cabbage 

 and through which the juices of the plant are sucked into the mouth of 

 the insect. It is this constant drain on the plant caused by thousands 

 of tiny beaks sucking out the juices, that produces the injury. The leaves 

 remain small, become deformed and rolled up, and finally wither and per- 

 haps die. The whole plant remains stunted, fails to head, and so becomes 

 worthless. Often, as a result of the injury, the plants are attacked with 

 the bacteria of decay and actually rot in the field. We have known whole 

 fields of cabbages destroyed by this pest, and large portions of other 

 fields rendered worthless for market. 



OTHER APHIDS 



There are many kinds, or species, of aphids and they occur on many 

 different plants. During some seasons, apple trees are badly infested 

 with plant lice that curl the leaves, stunt the new growth of the branches, 

 and cause small, knotty apples. The shining dark brown eggs of these 

 aphids are laid on the twigs and branches in the fall, where they may be 

 found at any time before the first of April. In the spring these eggs 

 hatch and the young gieen lice may be found all over the swelling buds. 



Currant bushes, rose bushes, peach trees, cherry trees, elm trees, and 

 other plants are often badly infested with aphids. Most of these aphids 

 are green in color, but some, like those on the cherry, are black, while 

 others are grayish or sometimes covered with a downy, cottony material. 



THE FRIENDS AND ENEMIES OF APHIDS 



Plant lice have the rather peculiar and interesting habit of secreting 

 a sweet liquid commonly known as honeydew. Often the flagstones in 

 sidewalks are wet beneath elm and maple trees from the drops of honey- 

 dew that have fallen down from aphids on the leaves. Ants are very 

 fond of this honeydew and carry it away to their nests for food. It is 

 seldom that one finds lice on a plant without finding them attended by 



