AND OTHER BUILDINGS 175 



laboratory, with cockroaches, the so-called "silver 

 fish," and the Angoumois grain moth. C. P. Hartley, 

 an assistant in the laboratory, had the building fumi- 

 gated with very excellent results. At the suggestion 

 of Dr. Webber the following statement of facts was 

 furnished by Mr. Hartley : 



' ' During the summer of 1901 one of the laboratories 

 of the United States Department of Agriculture became 

 badly infested with mice and insects of many kinds. 

 It was decided to try the efficacy of hydrocyanic acid 

 gas in ridding the building of these pests. This labora- 

 tory had become the abode of cockroaches, beetles, 

 crickets, moths, flies, etc., to some extent because it 

 was connected with greenhouses where these insects 

 abounded, but more especially because of seeds, fruits, 

 and plant specimens that were stored in the vari6us 

 rooms. The entire building, a two-story frame struc- 

 ture of eight rooms, was twice fumigated during the 

 latter part of the summer with such success that the 

 building was free from insects for the rest of the year. 

 The first fumigation was given the latter part of 

 August and freed the building for a week or more, 

 after which time many small roaches and other young 

 insects became noticeable which probably developed 

 from eggs in the building. 



* * For the first fumigation old stock potassium 

 cyanide from several sources and of various appear- 

 ances was used, but for the second, ten days later, 

 fresh material was used, and resulted in killing every 

 insect and mouse in the building. This fumigation 

 was started at four o'clock in the evening and the 

 building was kept closed until the next morning, when 



