190 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



using a fouutaiii pump or garden syringe. lu many instances, however, 

 these remedies are impracticable, for frequently tlie worms appear in 

 a field of grain so late in the season that the crop is only partially de- 

 stroyed. In some instances only the leaves and beards of the grain are 

 eaten by the worms, the straw and heads being too mature to be relished 

 by them. In such cases the destruction of the crop by the use of rollers 

 or poisons would be an expensive method of fighting the pest. And, 

 too, the use of rolleis often proves less effectual than would be expected. 

 If the soil be rough it is obvious that many worms would escape ; and 

 it was found by experiment on Long Island this year that even when 

 the surface was level the rollers became partially covered with masses 

 of tenacious mud, comi)osed of earth and the juices of the crushed 

 worms, so that the effect was much the same as though the ground had 

 been uneven. 



"When these remedies prove impracticable the second line of defense 

 remains, and if well carried out the result wiU not merely be the confin- 

 ing of the worms to the fields in which they appear, but the destruction 

 of them also when they attempt to migrate to other fields. This is done 

 by the means of ditches and pits dug around the infested field or that 

 to be protected. The ditches can be made quite rapidly. First plow a 

 furrow with the " land side" next to the field to be protected, and then 

 ■with a spade make this side of the furrow vertical, or, if the soil be com- 

 pact enough to admit of it, overhanging. When the ditch is completed, 

 holes should be dug in it from 1 foot to 18 inches deep and from 20 to 

 30 feet apart. The sides of these holes should also be vertical, or, if pos- 

 sible, overhanging. The worms, unable to climb up the vertical side of 

 the ditch, wiU crawl along the bottom of it and fall into the holes, where 

 they will soon perish. Where the soil is sandy, so that the ditch cannot 

 be made with a vertical side, it should be dug deeper than in other cases, 

 and the side made as nearly perpendicular as possible, so that when the 

 worms attempt to crawl up it the sand will crumble beneath them and 

 cause them to fall back again. The soil can be kept friable by drawing 

 a bundle of brush along the ditch, or by burning straw in it. 



The degree of success and the amount of labor attending the use of 

 this method of defense depend upon the promptness with which it is 

 adopted. K a close watch be kept of the grain fields and meadows 

 during late spring and early summer, the i)resence of the worms can be 

 detected before they begin to migrate. It will then be only necessary to 

 inclose, by means of ditches, those parts of the fields in which the worms 

 are found ; and frequently these localities are very limited. But if the 

 work be delayed until later in the season, after the worms have begun 

 to migrate, it will be found difficult to confine them, and it will prob- 

 ablj^ be necessary instead of this to siuTound by ditches the fields to be 

 protected, especially any fields of corn that may be in the vicinity of the 

 infested district. 



Numerous other remedies have been proposed, but we know of none 

 which are practicable, except on a small scale or under especially favor- 

 able conditions. 



The parasites of the army worm are very numerous, and benefit the 

 farmer to an almost incalculable extent. By far the most abundant is 

 the red-tailed Tachina fly {Nemoroxa leiicaniae, Kirkp.). This insect, 

 shown at PI. I, fig. 2, has much the appearance of the ordinary house- 

 fly, and is usually found in immense numbers wherever the army worm 

 abounds. The natural but interesting mistake has been made by some 

 of our correspondents of considering the red-tailed Tachina as the 

 progenitor of the army worm. The eggs of this Tachina are whit«, 



