OF WASHINGTON. 17 



collected at various points in Indiana, Pennsylvania, and Mich- 

 igan, and distributed to points in Georgia, Alabama, Missis- 

 sippi, and Missouri. The object of the transfers made from 

 northern to southern localities was to determine whether the 

 17-year period was governed by latitude and temperature. 

 A large quantity of eggs of the 13-year brood, also, was col- 

 lected in Mississippi and Missouri, and distributed to various 

 observers in New York, Iowa, Massachusetts, and Maine, the 

 intention being again to determine whether the 13-year period 

 was merely a matter of temperature. All the transfer plant- 

 ings of the 13-year brood failed, as did also the 17-year brood, 

 including plantings in Washington. The difficulty in these 

 cases seemed to have been in the lack of sufficient material and 

 the natural accidents and reduction in numbers which go on 

 steadily during the long 17-year or 13-year term. Neverthe- 

 less, it was possible to follow the plantings made in Washing- 

 ton for a considerable series of years before the larvae in the 

 soil practically disappeared. It is probable, however, that 

 some few adults actually emerged at the end of the 17-year 

 period, which, for the 17-year race experimented with in Wash- 

 ington, was in 1902. 



A much more promising experiment, because of more abund- 

 ant material, was instituted on the Department grounds in 

 1889 with the 17-year race which appeared in that year and 

 which had its return appearance during May and June of last 

 summer (1906). This brood is practically unrepresented in 

 the District of Columbia, and did not occur at all on the Depart- 

 ment grounds. A very large quantity of egg-infested twigs 

 was obtained from North Carolina, Long Island, Kentucky, 

 and Ohio — several cartloads altogether — and these were dis- 

 tributed under oak and other trees on the grounds of the 

 Department of Agriculture. The eggs in most instances were 

 hatching when received, and were placed under the trees in 

 the very best condition for the larvae to enter the soil, and 

 many thousands — probably hundreds of thousands — of larvae 

 actually went into the soil under these trees. This experiment 

 was made during the first year of the writer's connection with 

 the Bureau of Entomology, and the later examinations were 

 made chiefly under his direction. Three years after the plant- 

 ing, the soil under the trees where the egg-bearing twigs had 

 been distributed was found to be thickly filled with larvae, so 

 much so that a single spadeful of earth would often turn up 

 half a dozen or more. In the spring of 1897 the larvae had 

 reached the fourth stage and were still very abundant in the 

 soil. Examinations were made from time to time showing 

 these larvae to be still present in the soil about the trees where 

 the eggs had been distributed, going through the slow process 



