April, '19] FLINT, TURNER AND DAVIS: EXPERIMENTAL METHODS 



179 



of these problems pertained to our work with the Hessian fly, they have 

 a greater or less bearing on other entomological problems, especially 

 entomological problems of the corn and grain fields, and the summa- 

 rized results are here offered for the benefit of others working on similar 

 problems; also with the hope that any inaccuracies in our work may 

 be pointed out to us in order that a standard may be established which 

 will enable one to more easily compare work done by investigators in 

 different parts of the country. 



Methods of Making Comparative Counts of Infestation 



In the fall of 1917 several methods were tried^ in an infested wheat 

 field at Virden, 111., to determine means of obtaining accurate records 

 of infestation. Three systems were tried: the picking method, the 

 linear yard method, and half square yard. The first mentioned con- 

 sisted in stooping down and picking a plant at one side, one on the 

 opposite side and one in front or behind, in all cases the plants being 

 taken at random; this taking of three plants to be repeated after 

 walking about ten steps. In picking it was necessary to take the plant 

 from the side and not allow the hand to pass over the tops of the plants 

 in selecting one, since the uninfested plants are usually higher and an 

 inaccurate count will be obtained. Fifty plants were taken in this 

 way. By the second method, five linear yards were selected by tossing 

 a trowel five or ten yards ahead and examining all plants in the yard 

 from the point of the trowel. The half square yard was similarly 

 selected except that only two ( = one square yard or five linear yards) 

 were taken. 

 The results were as follows: 



Table I — Results of Counts by Different Methods, 1917 



From a general survey the actual infestation was 12 to 15 per cent, 

 and of the three methods used the picking method in this case gave 

 the best results. 



This fall (1918) more thorough counts were made- at Virden, lU. 

 In order to determine as nearly as possible the actual infestation of 

 the plot, every other yard of two wheat rows, one on each side of the 



' By Flint and Davis. 



* By Flint, Turner and Davis. 



