26 THE ORTHOPTERA OF MINNESOTA. 



half feet high. Over this frame a piece of canvas is stretch- 

 ed. This frame serves the important office of throwing back 

 all those locusts that otherwise jump clear over the 

 pan, and to throw them into the oil. The runners on which 

 the pan rests are usually made from saplings or small pieces 

 of board having an upward curve in front to prevent them 

 from catching in the ground. The front ends of the runners 

 are all fastened by screws to a cross-piece which is, in turn, 

 drawm by two ropes, one at each end. These ropes are joined 

 in front and fastened to a single-tree. Sometimes two 

 "hopper-dozers" are fastened to a long pole by means of 

 short ropes ; this is ver3' easil}^ drawn by one horse. Just in 

 front of the pan is fastened a piece of rope w^hich sw^eeps the 

 ground a few inches in advance and serves to stir up the 

 hoppers and make them jump into the pans. In the pan is 

 laid a piece of cloth, which is first thorough!}^ saturated wnth 

 water. About a pint of kerosene oil is then thrown in and 

 the upright slieet or sail of canvas is also moistened with it. 

 The machine is drawn over the fields or wherever the locusts 

 are thickest. In a short time it is usually partially filled 

 with dead or dying insects. 



The slightest touch of kerosene oil, either from the pan or 

 from the canvas sheet behind it, means death to the locust, 

 for the oil spreads over its body in the same w^ay that a single 

 drop of it wnll spread over a large surface of water. It seems 

 to produce a paralysis, which is first shown by the stiffening 

 of the legs. A very large proportion of the locusts that come 

 in contact with the oilinthepan immediately jump out again, 

 but they invariably die in the course of a few seconds or 

 minutes. Fig. 6 shows a hopper-dozer in operation in a 

 hayfield. A narrow strip is cut around the margin of 

 the field and the hopper-dozer is drawn around in this strip, 

 with great success. Fig. 7 shows two fastened together and 

 drawn side by side. Figs. 8 and 9 show tw^o other hopper- 

 dozers more in detail so as to enable anybody, even wnth but 

 little ingenuity, to make them. The nature of the ground 



