EXPERIMENT STATION BULLETINS. 493 



kept under observation at intervals for one day; none of the insects 

 sliowed any recovery. (See tables IV and V for the effect of carbon 

 tetrachloride upon reductases and catalases). This last charge of in- 

 secticide vapor was considered satisfactory; and following it, similar 

 fumigations wore made at intervals of about five weeks, on the average, 

 from May until October. The large room, in which the "fur room" was 

 located, was well ventilated and nothing of a disagreeable nature was 

 ever experienced from the fumigation. All the furs came through the 

 Summer in tine condition. The company management was so well pleas- 

 ed that the same method is being used with the furs again in the Sum- 

 mer of 1915. Moreover, Mr. Armstrong, who was in charge, reported 

 that this method of caring for the furs had proven to be cheaper than 

 'cold storage"; and in addition, it afforded the very great advantage of 

 convenience in having the furs where they were easily accessible. Car- 

 bon tetrachloride cost the company- twenty-seven cents per pound. 



C. HEAT AS AX INSECTICIDE, 



Finall}', suggestions relating to possible practice should certainly 

 call attention to heat as an insecticide. The effect of heat upon oxi- 

 dases, catalases and reductases in the tissues of P. cornntus and 

 various other insects has alreadj' been given earlier in this paper. No 

 more efficient means than heat was found for destroj'ing the activi- 

 ties of these three agencies of the tissue cells; it was shown that 

 when specimens of P. cornutus were killed by the least degree of 

 heat that could be effectively used, the activities of reductases, oxidases, 

 and catalases were injured in a greater or less degree. The effect of dif- 

 ferent degrees of heat in coagulating the various soluble proteins in ani- 

 mal tissues is well known. It should )>(> added here that fatal injury to 

 the insects, and noticeable injury to one or more of the three kinds of 

 enzyme-like bodies named, seemed to occur just before the first aggluti- 

 nation of protein took place. The reductase was the most susceptible. 

 In case of clear, filtered water extracts of the tissues of P. cornutus, 

 which were heated up very slowly and gradually, the soluble catalase 

 showed its greatest loss in activity earlier than the guaiac oxidase. The 

 latter lost its principal activity at the moment of separation of the chief 

 or largest protein precipitate. 



The fatal temperature, in the case of insects, varied considerably with 

 the species and with the length of time the insects were exposed. No 

 insects were tried, however (in small enclosures), which required a 

 temperature of more than 122° F. maintained for a period of 

 three hours to cause death; and at that temperature, death 

 usually resulted quickly. Now, 122° F. is a comparatively low 

 temperature and many plants can stand exposure to even higher temper- 

 atures for several minutes without appreciable injury. It is very well 

 known that cabbage can endure hot water or hot soapsuds much better 

 than can the common "cabbage worm." In fact, when cabbage is head- 

 ing, hardly any safer or better method for killing cabbage-worms in the 

 home garden is xn^acticed than the use of hot soapsuds. During the last 

 five or six years, Professor Dean of the Kansas State Agricultural Col- 

 lege and Experiment Station has introduced heat as a comparatively 

 cheap and efficient method of controlling all classes of mill-infesting in- 



