305 



all were in the adult stage. It was found that the activity of the 

 insects made it unusually difficult to conduct field experiments on a 

 small scale, it being necessary to make a Hberal allowance for errors 

 and variations and to draw no conclusions except through the grouping 

 of records or from observations repeated several times. 



The baits to be tested were prepared in the laboratory and the same 

 tests were conducted simultaneously by tw^o observers working in 

 different fields, observations being made at intervals of fifteen minutes. 



The standard mixture was prepared according to the formula : bran 

 25 lb., 5 lemons, 2 qt. molasses, 1 lb. Paris green and water to 

 make a crumbly mixture, and this was varied by the substitution of 

 oranges, tomatoes and canteloups for oranges, the replacement of 

 bran by sawdust and the omission of molasses. 



The results showed that canteloup was the most attractive fruit 

 and lemons the least ; that the use of molasses did not increase the 

 effectiveness of the baits ; that pine sawdust was much inferior to 

 bran, baits prepared with it being only about half as effective. The 

 bran available in Arizona however contains a large proportion of 

 fine material and the use of J to h sawdust gives a mixture that is 

 much easier to distribute in the field. 



Observations were also made on the distance that poisoned grass- 

 hoppers travel, a fact that it is sometimes important to know, and it 

 was found that none could move more than 27| yds. from the poisoned 

 plot. 31. differentialis feeds most actively during the warmer parts 

 of the day and less actively towards night, and similarly the best 

 results from feeding the grasshopper, Eucoptolophus subgracilis, Caudell, 

 with poisoned bran mash, were obtained between the hours of 3 p.m. 

 and 3.30 p.m. 



Calculations based on the weight of freshly-cut lucerne eaten by 

 adults of M. differentialis enclosed in a wire screen cage showed that 

 one individual per square yard may destroy the equivalent of 3 lb. 

 lucerne hay per acre per day. In a 40-acre field a moderate infesta- 

 tion averaging 16| hoppers per yard may destroy the equivalent of 

 1 ton of lucerne hay per day. It is evidently very profitable therefore 

 to poison these grasshoppers, even when they average as few as 5 per 

 square yard. 



Plint (W. p.). Suggestions for a New Method of Destroying Chinch- 

 bugs. — Jl. Econ. Entom., Concord, N.H.,xi, no. 2, April 1918, 

 pp. 186-188. 



The fact that the chinch bug [Blissus leucojjterus] collects in large 

 numbers on any moist object, or on the ground where water has been 

 spilled, suggests a possible means of control by bait moistened with 

 poisoned water. 



Laboratory experiments with bran wetted with sodium arsenite of 

 various strengths gave good results, a high percentage of the insects 

 dying in a few hours. The addition of syrup to the solutions did 

 not have the effect of making them more attractive. During the follow- 

 ing spring similar experiments were made in the field, the substances 

 used being wetted with sodium arsenite, lead acetate and sodium 

 cyanide at strengths of from | ounce to 2 ounces per U.S. gal. water. 

 The sodium arsenite solutions were not very effective at the strengths 

 used, and they also seemed to have a slightly repellent effect on the 



(C479) O 



