CONTROL OF MORMON CRICKET WITH POISONED BAIT 15 



sity for an efficient poisoned bait. Work was begun in 1935 and 

 continued through 1939 to develop a satisfactory bait for the Mormon 

 cricket. 



In the earliest tests crickets were caught and confined in large en- 

 closures where they were given the poisoned bait. This did not give 

 the crickets enough choice of food, so beginning in 1937 tests were 

 made with a smaller pen, and the crickets, after they had been per- 

 mitted to feed normally, moved naturally forward and were directed 

 by converging sheet-metal barriers (wings) into a chute which led 

 them either directly to the observation pen or to a cage from which 

 they were transferred to the pen. 



The tests in 1935 showed standard bran to be the best carrier. The 

 tests in 1936 showed that attractants do not add to the efficiency of the 

 bait. Sodium fluosilicate was used for the first time that year. In 

 1937 sodium fluosilicate at the rate of 4 pounds per 100 pounds of 

 bran was used successfully in an oil bait under the improved system 

 of experimentation and proved superior to a bait containing sodium 

 arsenite. It was found in 1938 that the oil was not necessary and 

 that 2 pounds of sodium fluosilicate is not sufficient to give the maxi- 

 mum kill. Although a bait containing 2 gallons of cane molasses gave 

 a slightly greater mortality than the one containing no attractant, it 

 was evident that the small increase in efficiency did not warrant the 

 additional cost of the molasses. In these tests sodium arsenite was 

 proved to be repellent to Mormon crickets. 



The tests of 1939 further substantiated the fact that standard bran 

 is the best carrier, although in large-scale baiting tests in South Dakota 

 and Wyoming high mortalities were obtained with a bait containing 

 1 part of mill-run bran to 3 parts of sawdust. Sodium fluosilicate, at 

 the rate of 3 pounds per 100 pounds of bran, proved as effective as 4 

 pounds against both nymphs and adults in 1 1 replications by wing-pen 

 tests. This material and sodium fluoride proved more effective than 

 synthetic cryolite or calcium fluoride. According to these tests, 

 crude arsenic at the rate of 4 pounds per 100 pounds of bran is not 

 distasteful to the crickets and may be substituted for the sodium fluo- 

 silicate. However, the danger to livestock from a bait containing 

 crude arsenic is much greater than from one containing sodium fluo- 

 silicate. 



Pan baiting tests conducted in 1938 on adult crickets and also in 

 1939 on nymphs showed that feeding is so closely correlated with 

 migrations that it is possible to recommend to farmers and other con- 

 trol units that the bait should be spread only while the crickets are 

 migrating. 



Large-scale baiting tests in 1938 and 1939 proved conclusively that 

 effective and economical control of both nymphs and adults can be 

 obtained by the proper use of sodium fluosilicate bait with standard 

 bran or, under restricted conditions, with mill-run bran and sawdust 

 as the carrier. 



