340 Report of the Department of Entomology of the 



METHODS. 



At the time the work was planned, no data were available regarding 

 previous efforts to kill hibernating larva? of the brown-tail moth by 

 fumigation. There were, however, conflicting rumors regarding the 

 success or failure of certain preliminary experiments conducted in 

 this and other states. The writer inferred that most of the prelimi- 

 nary tests would be conducted in the laboratory while in many 

 nursery establishments the fumigatorium is out-of-doors. To avoid 

 confusion regarding the particular conditions under which the work 

 was done a number of fumigators were arranged so that the work 

 could be carried on at different temperatures. The experiments 

 herein described include only those made with larvae that had been 

 separated from the nest. The method followed was to dissect the 

 caterpillars out of the nest, and place them on a cheesecloth-covered 

 wire frame. The container was placed near the center of the fumi- 

 gatorium during the period of treatment. An arrangement to effect 

 the combination of the chemicals after the closure of the fumigator 

 was used in practically all tests. Following fumigation the con- 

 dition of the larvse was noted and the receptacle carrying the cater- 

 pillars placed under a bell jar, so that they might be kept under 

 observation, other examinations being made during the next two or 

 three days. If at any time subsequent to fumigation an individual 

 showed signs of life it was counted as alive. The fumigators, which 

 were designated by letters, are briefly described as follows: 



A — Cubic contents 3.53 feet. A wooden box, made of tongued and grooved boards. 

 Heavily coated on interior with hard paraffin. 



B — Cubic contents 21.2 cubic feet. A wooden box lined with two thicknesses of 

 glazed paper. 



C — Cubic contents 31.5 cubic feet. Made of tongued and grooved material and 

 lined with two thicknesses of building paper. 



D — Cubic contents 17.6 cubic feet. Made of wood and coated on the interior with 



paint and shellac. 

 Bell jar. — Cubic contents 64S.62 cubic inches. Made dark by means of a metal 

 cylinder. 



FUMIGATION EXPERIMENTS. 



In addition to preliminary work using glass fruit jars, and some 

 final checking up in which one of the large nursery fumigatoriums 

 was employed, more than a hundred separate experiments with 

 insects were made. Besides these, numerous experiments were 

 carried out to determine the effects of similar charges of gas on the 

 various kinds of seedlings. The experiments with caterpillars have 

 been classified according to the amount of cyanide used per cubic 

 foot in each fumigation. For the purpose of discussing the effects 



