HEMIPTERA: THE TRUE BUGS 87 



upon which they fix themselves and secrete a larger scale. 

 They remain on the twigs through the winter, and the 

 following spring complete their growth, produce the 

 cottony mass within which they lay their eggs, and finally 

 die. . There is thus but one brood each year. Fortunately 

 this insect, as well as most other members of this family, is 

 commonly kept in check by its parasitic and other enemies. 

 The most important of these are small, black, four-winged 

 chalcid flies and various species of ladybird beetles. 



The Aphides or Plant Lice 



From the point of view of their destructiveness, the 

 Aphides or Plant Lice form one of the most important 

 families, not only of the true bugs, but of all insects. 

 During very recent years a single species affecting grain 

 has caused a loss of more than a million dollars in one 

 state in a single year. There are a great many species of 

 these little pests, of which the Green Flies of house plants 

 are familiar examples. They infest nearly all kinds of 

 crops, sucking the sap through their pointed beaks and 

 often causing enormous losses. 



The life histories of the various species of Aphides are 

 quite similar. A good illustration is found in that of the 

 Spring-grain Aphis which has attracted much attention on 

 account of its damage to grain crops. Pictures of its vari- 

 ous stages much magnified are shown on the next page. 

 In many localities, it has been known as the "Green Bug." 

 It is especially abundant in the more southern rather than 

 the far northern states. 



Under normal conditions the Spring-grain Aphis passes 

 the winter in the condition of the egg, attached to leaves or 

 stalks of various grains and grasses. Early in the spring, 

 these eggs hatch into small plant lice that suck the sap 



