HEMIPTERA. 197 



days of summer. This form requires two years to come to 

 its full maturity, but its cousin, the seventeen-year locust, 

 requires, typically, seventeen years from the time the eggs 

 are laid until the animals are ready to lay another series of 

 eggs. These eggs are laid in the twigs of trees. The 

 young when hatched from these eggs drop to the ground, 

 and, burrowing beneath its surface, spend the next seven- 

 teen years * sucking the juices of the roots of the trees. 



Another group of Homopterans are the " spittle-in- 

 sects," small forms which, settling upon a blade of grass or 

 twig of shrub, soon surround themselves with a frothy mass. 

 They suck the juices of the plant, and after having token 

 out what they desire eject the rest as a mass of foam. 

 Examine one of these bits of froth and you will find the 

 immature bug inside. Allied to them are the tree-hoppers 

 and leaf -hoppers, so common and so injurious to vegetation. 



The plant-lice deserve a little more attention. They 

 occur on almost every kind of plant, sucking its juices and 

 reproducing as rapidly as possible. One does but little 

 damage, but the havoc wrought by thousands is very con- 

 siderable. In the summer the colonies of these forms will 

 be found to be largely wingless, and these wingless forms 

 are all females capable of reproduction without males. In 

 some species they lay eggs, in others they bring forth liv- 

 ing young. These in time reproduce in the same way, and 

 so rapidly do they increase that one plant-louse may be the 

 progenitor of 100,000,000 in five generations. At the 

 close of the season appear the true sexual forms, the males 

 always winged. These sexual forms produce eggs which 

 last through the winter. All of the plant-lice are destruc- 

 tive to vegetation, and some, like the Phylloxera of the 

 grape, are extremely so. 



* In the South the period is thirteen years, in the North seventeen. 



