CHAPTER XXrV 



CONTROL OF INSECT PESTS BY NATURAL FACTORS 



In this discussion we shall consider very briefly 

 the natural factors which help in the control of 

 parasitic insects. 



(a) Beneficial Predacious Insects. It is fortunate 

 that nature always provides its own remedies. If 

 insect pests were not kept in check by natural enemies 

 the trucker who does not spray would be faced by 

 tremendous odds in attempting to raise crops. The 

 natural and beneficial enemies may be grouped, first, 

 into parasites wbich develop within the body of the 

 host, and second, predacious or those which feed 

 externally. 



I. Of the first group may be mentioned a small 

 wasp-like insect, Lysiphlebtis testaceipes. This is no 

 doubt an important parasite, which greatly helps to 

 keep the green Aphis in check. Its life history was 

 originally worked out by Webster, ^ and may be briefly 

 summarized as follows : 



A mature female thrusts her ovipositor into the 

 upper side of the Aphis and deposits a single egg 



' U. S. Dept. of Agr. Bur. of Entomology Bui., no, 1912. 



375 



