94 NEW YORK STATE MUSEUM 



placed inside the fruit jar, and on these a circular piece of 

 corrugated cardboard so that the latter could not come in direct 

 contact with the glass bottom. The fruit jar, in addition, had 

 the lower half lined by corrugated paper in such a way that it 

 was impossible for the insects to come in direct contact with 

 the heated glass walls. The thermometer rested lightly upon 

 this cardboard bottom, the whole being covered with cheese- 

 cloth as before. 



Experiments 9 to 13 were conducted in a photographer's 

 dark room about five feet five inches by four feet eleven and one- 

 half inches and eleven feet high, the necessary heat being secured 

 from a gas heater and a gas plate. The insects were placed in card- 

 board cylinders with netting at each end, or in a lantern globe simi- 

 larly inclosed. One was put upon the floor, a second on a shelf 

 about four feet high and just inside of a window, so that develop- 

 ments could be watched, while the third was placed upon a higher 

 shelf some six feet from the floor. The observations in experiments 

 10 to 13 inclusive, tabulated below, relate to the insects on the shelf, 

 since they were the only ones that could be watched. Owing to 

 the small dimensions of the dark room and the rather wide 

 shelves, it was found that there was a considerable difference 

 between the temperature at the floor and five feet above. In 

 experiment 13, for example, a temperature of over' 125° was 

 maintained five feet from the floor for more than five hours, 

 while a maximum thermometer located on the floor registered 

 but 112°. 



Observation, whether the insects were in vials, fruit jars or 

 the relatively much larger dark room, showed that the cock- 

 roaches became uneasy when the temperature reached about 

 112° to II4°F; they exhibited evident signs of distress at 

 116° or thereabouts and succumbed at a temperature of about 

 120°. This is a comparatively moderate heat and it would 

 seem entirely practical, in the case of hotel kitchens and similar 

 places where there must of necessity be a good sized heating 

 plant, to destroy the pests with this rather moderate temperature.' 

 In practice it would be unsafe to plan for less than thirty minutes 

 at a temperature of 120° if one would obtain satisfactory results. 

 It might be necessary to prolong this period even more in 

 apartments where the insects could retreat in cracks or take 

 refuge under bagging or similar material which would afiford 

 some shelter from the heat. It is perhaps unnecessary to add 

 that the filling of all cracks and crevices would immensely 



