182 



different from that of others, so that only general statements 

 for the group as a whole can be made. 



As a rule, plant lice pass the winter in the egg stage, the 

 eggs being attached to the stem or twigs of the food plant. 

 In the spring the eggs hatch, and the tiny aphids, which are 

 green, brown or black, soft-bodied, wingless forms, with six 

 legs, begin to feed, sucking the juices from the twigs or 

 leaves. This is done by means of a pointed beak, the tip of 

 which is pushed through the bark or epidermis till it reaches 

 the sap. In the course of a few days each little aphid be- 

 comes adult, and begins to produce living young at the rate 

 of three or four nearly every day. These in their turn feed, 

 grow and reproduce, and in this way many generations ap- 

 pear during the summer. One or more of these generations 

 may develop wings and pass to other plants, in this way 

 spreading over the entire region. In the fall the last genera- 

 tion does not produce living young, but lays eggs instead, 

 and these winter over, hatching the following spring. 



The rapidity with which plant lice increase is of impor- 

 tance, as but a short time is required after the first individ- 

 uals appear for a plant to swarm with them ; and when this 

 occurs, treatment becomes more difficult. This is because in 

 many cases the effect of their feeding is to cause the leaves 

 on which they are to curl, thus protecting the lice so that they 

 cannot be reached by a spray. 



Plant lice produce a sweet, sticky fluid, known as honey- 

 dew, from two small tubes on the upper side of the body, and 

 ants are very fond of this, visiting the lice and gathering it 

 from them. If the honey-dew falls on the leaves and twigs, 

 it makes them sticky, and it is sometimes produced so abun- 

 dantly as to fall to the ground with a pattering sound like 

 rain. This substance forms an excellent place for the growth 

 of fungus, which turns the honey-dew black, and accounts 

 for leaves and twigs having a smutty appearance, particu- 

 larly in the late fall and early spring. 



