104 



PROTECTION OF PLANTS, 1915-16 



Injurious Insects 



The insects that affect farm crops may be classified into (1) those 

 that are periodically injurious, and (2) those that are always present and do 

 more or less damage every year. In the first class can be placed the Hessian 

 Fly, the Wheat-stem Maggot, the Joint Worm, Grasshoppers and Army 

 Worm, Western Wheat Stem Saw-fly; and in the second class, Wireworms, 

 White Grubs, Cutworms and Plant Lice. 



The Hessian fly, Mayeliola destructor (Say). Healthy wheat stock at left and infested stock at right; a, egg- 



b, larva; c, puparium or "flaxseed"; d, pupa exposed; e, adult female laying eggs;/, female; g, male; 



/;, puparia or "flaxseed" in natural position between leaves and stalk; i, parasite 



(Merisus destructor). (Slightly enlarged, excepting e, which is smaller 



than natural). (After Riley, Burgess and Forbes). 



