22 THE ORTHOPTERA OF MINNESOTA. 



All the eggs experimented with were in pods, which 

 were in no way injured or broken. 



To guard against any lateral movements of the youtig 

 locusts, and to prevent them from reaching the surface of 

 the soil near the sides of the pots, where cracks in the soil 

 w^ould naturally form by contraction of the earth, the sur- 

 face of this part of the soil was covered with a tight fitting 

 ring of oiled cardboard. All the egg-pods were carefully 

 planted in or near the center. Lifting up later the ring of 

 cardboard, many locusts were found under it, showing that 

 they had tried hard to reach the surface by digging in a 

 horizontal direction towards the least compressed soil. 



One thousand eggs, either single ones or in twos and 

 threes, but all free from any mucous covering, were planted 

 to a depth of one inch and a half The soil above them was 

 gently compressed and kept moist. Only 103 young lo- 

 custs managed to reach the surface. As this happened 

 v^'^hile the writer was away from the office, he can not be 

 certain whether or not some of them came up from below 

 the ring of cardboard near the inner rim of the flower pot, 

 this board having warped considerably on account of the 

 moisture of the soil. 



Early in July, after all the experiments had been finished, 

 the soil from the various flower pots was thrown into a 

 large box and w^as thoroughly loosened with the fingers. 

 In consequence of this seven young locusts made their ap- 

 pearance, showing that some of the eggs, or of the j^oung 

 insects, had retained their vitality up to that time. 



Plowing. The chief and safest method to combat lo- 

 custs consists in plowing the land known to contain their 

 eggs. By carefulU" investigating the suspected fields in a 

 number of places an approximate knowledge can be gained 

 as to the number of eggs they contain. If a field has thus 

 been ascertained to contain eggs it should be plowed at 

 least five to six inches deep. If done properly, and in time, the 

 very great majority of eggs are prevented from hatching, or 



