21 



Why heavy damage should have been done to seed-corn at Nor- 

 mal because of rains, while rainy weather did no such harm at Le Roy 

 or Chenoa, it is impossible now to determine for the lack of more 

 specific information concerning the situation at those places. 



Laboratory Experiments with the Effects of Repellents 



ON Ants 



The substances used in 1907 and 1908 in field experiments against 

 the corn-field ant had proved unsatisfactory, partly by reason of the 

 uncertainty of their effect on the insects, but largely also because of 

 the injury to seed-corn in wet weather. In the case of the oil of 

 lemon an additional difficulty was an insufficient supply of the oil 

 and the consequent certainty that the price would be put up to a 

 prohibitive figure if there was anything like a general demand for it 

 at planting time. A considerable series of experiments on ants was 

 consequently undertaken in the beginning of 1909 with a large 

 variety of possibly available repellents, with a view to a selection of 

 those most efficient and most readily obtainable, for further use in 

 the field. As it was desirable that the repellent effect should be got 

 without the substance chosen actually touching the seed, the fluids 

 were mixed with sand or other similar substance of a kind to be 

 applied in the field by means of a fertilizer-dropper attached to the 

 planter and dropping a powdered fertilizer beside or over the hill. 



All the experiments reported in this section were made by Mr. 

 Maurice C. Tanquary, a temporary assistant of the office, also, at the 

 time, a graduate student in the University of Illinois. His work 

 began January 13, 1909, and was carried on at irregular intervals 

 until the 30th of the following June. In all of them, established 

 colonies of ants were used, each consisting of worker ants and larvae, 

 and sometimes containing also a queen. As many previous experi- 

 ments with the corn-field ant had shown that it has a strong prefer- 

 ence for orange light, in which, altho its movements can be plainly 

 seen by us, it seems to act as if it were itself in the dark, and as the 

 worker ants are extremely devoted to the care of the larvae of their 

 species, an apparatus was arranged which should take advantage of 

 these two facts to afford a place of comfortable and attractive resort 

 such that the repellent effect of the substances tested might be shown 

 by driving the ants from these comfortable quarters into others less 

 desirable. It was thought especially that, if they were forced to 

 desert their larvae, the distance to which they were driven by the 

 repellents and the length of time elapsing before they returned to the 



