234 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



the hurricane of the fall of 1915, which so injured the experimental 

 orchards and eliminated the fruit as to make continuation of the 

 work at this time impracticable. In the meantime, the main feature 

 of this work, which relates to the Argentine ant, has been carried on 

 in southern California and is nearing completion. A bulletin giving 

 the results thus far obtained is in course of preparation. 



Insects affecting tropical and subtropical fruits and plants in 

 greenhouses. — A very important line of experimental work has been 

 conducted during the year which will eventually result in the stand- 

 ardizing of greenhouse insect control. Greenhouse fumigation with 

 hydrocyanic-acid gas has been standardized, particularly in rela- 

 tion to the dosage which can be used safely for various kinds of 

 plants and the strength of gas necessary for the control of different 

 greenhouse insect pests. 



Mediterranean fruit fly and melon fly. — The control and in- 

 spection of fruits shipped from the Hawaiian Islands to the main- 

 land of the United States are conducted in cooperation with the 

 Federal Horticultural Board. During the year the biological studies 

 of the Mediterranean fruit fly and the melon fly and the relation of 

 these pests to bananas and pineapples, the two important export 

 fruits of Hawaii, were completed. The investigation of the useful- 

 ness of introduced parasites has been continued and has been en- 

 larged to include thorough biological studies. During the year there 

 have been published the results of experiments on the control of fruit 

 flies by cold-storage temperatures and parasites, and on the status of 

 the banana as a host fruit, and two bulletins have been prepared in 

 which have been summarized the results of the investigational work 

 of the last three years. 



BEE-CULTURE INVESTIGATIONS. 



The work in bee culture during the year was chiefly a continua- 

 tion of the lines of investigation previously instituted. As in the 

 preceding year, this work has been conducted at the branch labora- 

 tory and apiary at Drummond, Md., a suburb of Washington, under 

 the supervision of Dr. E. F. Phillips. 



Wintering of bees. — A continuation of investigations on the win- 

 tering of bees has been the principal work of the office during the 

 past year. Because of lack of facilities for extensive experimenta- 

 tion in cellar wintering, the chief emphasis again has been placed on 

 outside wintering. The work on colonies packed in various ways has 

 been continued, but most of the colonies in the experimental apiary 

 were wintered with good results in groups of four, heavily insulated. 

 The various commercial insulated hives used in the United States 

 were tested in the apiary, but were all found to provide insufficient 

 insulation for a climate even as mild as that of Washington. Previ- 

 ous to using these commercial insulated hives for wintering bees they 

 were tested for comparison as to thermal conductivity. It was found 

 that in all of them the part where the most heat is lost is the un- 

 protected hive bottom, and because of this common weakness these 

 hives are practically identical in value as protection for bees. The 

 insulation of the bottoms of these hives was found to increase their 



