CEREAL PESTS INSECTS 487 



with the land side next to the field to be protected, and 

 dragging a log through the furrow to keep the earth 

 stirred and kill the worms which have accumulated in 

 the ditch. Another remedy is to poison a strip of pasture 

 or crop heavily with Paris green or London purple in 

 advance of the traveling army of worms. A very effec- 

 tive poisoned bait is made as follows : 50 pounds wheat 

 bran, 2 pounds paris green, 2 gallons sorghum or cattle 

 molasses, 3 oranges or lemons. The paris green is 

 thoroughly mixed with the bran while dry, the molasses 

 is then added, together with the fruit juice, and the mass 

 kneaded into a stiff dough. The small pieces of this, on 

 crumbling, are then scattered thinly over the infested 

 fields. It may be sown over large areas by means of 

 the broadcast endgate seeder (351). The method can 

 be followed where it is not advisable to spray with arsen- 

 icals. By disking infested fields late in the fall, winter, or 

 early in the spring, many pupse can be killed. There 

 are natural enemies that keep the worm in check, such 

 as the parasitic tachina flies. As many as 50 eggs of a 

 species of tachina are attached sometimes to a single 

 caterpillar. 



531. The sawflies. There are a number of 4-winged 

 flies called sawflies found in grain fields, usually in 

 wheat. They are so named because of the saw-like ovi- 

 positor of the adult female, with which incisions are made 

 in the tissues of plants for the insertion of eggs. Most 

 of the sawflies are of little economic importance, and only 

 occasionally migrate from wild grasses to wheat. A few 

 of them sometimes do considerable damage, and are of 2 

 classes, stem borers and leaf feeders. 



The European wheat sawfly (Cephus pygmoeus, Linn.), an 

 important species, has caused little or no loss so far in this 



