82 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



checks. The weather of the spring was dryer than usual, but not suf- 

 ficiently so to delay noticeably the sprouting of the seed or the growth 

 of the plants. A preliminary examination of the field showed an av- 

 erage of 512 colonies of Lasius amerkanus to each acre, equivalent to 

 1,840,000 adult and larval ants. 



Six weeks after planting, hills were dug up freely in both check 

 and experimental strips, and all the ants and aphids were counted in 

 each case, with the general result that the strip planted with seed 

 which had been treated with carbolic acid showed a reduction of 14% 

 in number of aphids per hundred hills of corn, and 17% in number 

 of ants; that treated with formalin showed a reduction of 60% in 

 number of aphids and 48% in number of ants; the kerosene strip, a 

 reduction of 84% in aphids and 58% in ants; and the strip planted 

 with seed treated with the oil of lemon, a reduction of 89% in aphids 

 and 79% in number of ants. The reduction in number of hills in- 

 fested at this time was as follows : Carbolic acid, 15% ; formalin, 

 44%; kerosene, 47%; oil of lemon, 58%. At the end of ten weeks 

 the average height of stalks in the central row of a check strip — meas- 

 uring only the highest stalk in a hill as it stood, without stretching it 

 up — was 35 inches. The corresponding average of stalks in an experi- 

 mental strip was 60 inches. On September 21, nineteen weeks after 

 planting, a check row contained 330 hills with corn ; a row from the oil 

 of lemon strip, 326 ; a row from the kerosene strip, 282 — a loss of 48 

 hills, due doubtless to the effect of the kerosene on the seed. The stalks 

 at this time were 620 per row in the check, 641 in the plot treated with 

 oil of lemon, and 510 in that treated with kerosene — a gain of 21 stalks, 

 apparently due to the lemon treatment, and a loss of 110, due to the 

 kerosene treatment. Ears at this time averaged 413 per hundred hills 

 for the check strip, 526 to the hundred for the lemon strip, and 455 

 per hundred for the kerosene — a gain, from the use of lemon, of 113 

 ears and from the use of kerosene, of 42. The gain in number of 

 ears was thus practically 20% where oil of lemon was used. There 

 was also a notable difference in the size of the stalks and the ears in 

 all the experimental strips as compared with the checks. 



Similar and more extensive experiments made with a variety of more 

 or less promising substances during the spring of 1907 were virtually 

 without result, owing to heavy and repeated rains during the plant- 

 ing season and for some time subsequent, the effect of which was to re- 

 move all traces of the repellent substances from the planted seed and 

 at the same time to suppress almost completely the corn root-aphis in 

 the field. Trial plantings, made by farmers in various parts of the 

 state, of seed-corn treated with oil of lemon, have in some cases re- 



