496 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



The Grain-aphis, or Green -bug (Toxoptera graminum). 

 This little green plant-louse sometimes seriously injures young 

 wheat plants by sucking out the sap. They do most damage 

 in the south, where the open winters often allow them to feed 

 and reproduce during the whole year. In such instances they 

 become so abundant on the winter wheat that whole crops may 

 be ruined as early as March or April. As long as the tempera- 

 ture is above 56 F. the green-bugs are held in check by a 

 minute wasp-like parasite, Lysiphlebus testaceipes, and it is 

 only during the winter time, when it is warm enough for the 

 pest to breed but too cold for the parasite, that the plant-lice 

 become destructively abundant. Oats are the favorite food 

 of these aphids, and they seldom do much damage in places 

 where volunteer oats are not allowed to grow. 



When small injured spots appear in the field late in the winter 

 the green-bugs in such areas should be killed by spraying with 

 kerosene emulsion, or by burning straw over them, or by plow- 

 ing under the infected grain. 



STORED GRAIN 



Stored grains are often attacked by the larvae of beetles or 

 moths, and unless preventive measures are adopted much of 

 the grain may be destroyed. 



The Grain- weevil (Calandra granarid) , and the Rice -weevil 

 (C. oryza). Weevils are usually the most common pests of 

 stored grain. They are small beetles with long snouts, with 

 which they puncture the grain, thus making a place where the 

 egg may be inserted. The larvae are short, thick, legless grubs 

 that feed in the grain until ready to pupate. The beetles, too, 

 feed on the grain, and as they increase in numbers very rapidly 

 a slight infestation may soon assume serious proportions. 

 Grain should be stored only in clean, tight bins. If this pre- 

 caution is taken but Uttle loss will be suffered on account of 

 these pests. If, however, the grain becomes infested, it should 

 be treated with carbon bisulphide, using about five pounds for 

 every 1000 cubic feet, or even more if the room is not tight. 

 Best results will be obtained if the temperature is 70 F. or 

 higher. Dishes containing the liquid, or cotton or waste 



