EXPERIMENT STATION BULLETINS. 589 



on attaining their full size transform to the pupal stage; to do this 

 they either go just beneath the surface of the ground or secrete them- 

 selves under rubbish, The pupa is brown in color and about three- 

 fourths of an inch in length. 



The adult winged-moth (Fig. 18a), the parent of the caterpillars, is a 

 clay-colored "miller" about an inch long, having at the center of each 

 front-wing a distinct white spot. The veins and margins of the hind- 

 wings are slightly darker and the front-wings are sprinkled with dark 

 scales. 



NATURAL ENEMIES. 



Fortunately the army-worm has many insect enemies that feed on it. 

 Several hies belonging to the Tachinidse and some little, wasp-like in- 

 sects belonging to the Hymenoptera. The good work done by these in- 

 sects has much to do with keeping down the ravages of the army-worm. 

 The tachina-flies lay little china-like eggs on the skin, usually near the 

 neck, and these eggs hatch into grubs that burrow in through the skin 

 and feed on the body of the living host. Whenever these eggs are seen to 

 be plentiful, it is a pretty good sign that the worm will soon be in sub- 

 jection again. 



REMEDIES. 



While it is difficult to apply any remedies that will save the field 

 already infested, it is usually possible to prevent the migration into 

 hitherto uninfested fields. To this end the entire infested area should 

 be enclosed, either by barriers, ditches or furrows. The cheapest method 

 and the one most quickly, applied, is that of plowing furrows around 

 the infested region. Four or five deep furrows should be plowed about 

 six feet apart, turning the furrow toward the worms. The land side of 

 the furrow should then be straightened with a shovel, and sometimes it 

 is found advantageous to dig pits at intervals along the line, or better, 

 to dig steep holes with a post-hole digger at intervals. The caterpillars 

 in trying to march, will fall into the furrows, and in trying to climb up 

 the steep side they will work along until they fall into the pits. Many 

 will climb up the steep side of the furrow, but these will encounter the 

 second ditch, and so on. When the first few ditches get well filled, they 

 may be turned under by another furrow. As the worms work most in 

 the night and during rainy weather, it is well to have several furrows 

 where practicable, so that they will not require such constant watching. 

 Sometimes the nature of the ground or of the surroundings renders it 

 impossible to plow more than one furrow. In such a case a post may be 

 attached to a rope and dragged along the furrow as the worms collect, 

 crushing the worms and smoothing the furrow. 



It is very difficult to say with any degree of certainty just when army- 

 worms w T ill become troublesome, but outbreaks are usually preceded by 

 a wet spring, and two army-worm years seldom come in succession. 

 It is well to watch the grain fields carefully, and whenever the leaves 

 are seen to be disappearing and the little caterpillars are found to be 

 plentiful, the field should be destroyed before the caterpillars are large 

 enough to migrate. 



