68 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



stopped before a temperature has been reached which will injure the 

 cereal (between 90'' and 100° C). 



Since high temperature thermometers are not available for all house- 

 keepers, a mixture of carnauba wax and paraffin has been devised 

 which melts at the proper temperature for the surface of the flour. It 

 is not the exact point at which the wax melts, but the melting of the 

 piece of wax to a grease spot that is taken as the indicator. Therefore 

 the piece of wax measures, not only the temperature attained, but also 

 the time required for a certain amount of heat conduction, until the 

 entire piece of wax has melted. Since temperature and time for heat 

 conduction are the factors concerned in the uniform heating of the 

 cereal, the wax may be even more satisfactory than thermometers, 

 which register temperature only. 



In practice, the method has proved to be very satisfactory, and is 

 now being used in several states. When methods of rapid transit are 

 followed systematically by the heating of cereals as soon as they are 

 received by the consuming public, the losses which insects cause to 

 these flours and cereals will be reduced to a minimum. 



There are, however, certain difficulties to be contended with in the 

 introduction of this method. The public must be acquainted with the 

 method and impressed with its importance; in this the Federal Food 

 Administration for Minnesota has cooperated. The wax must be 

 made available for all, and in this matter the wholesale grocers co- 

 operated in supplying their trade throughout the state, yet there were 

 frequent complaints from those who were unable to obtain wax. To 

 supply the demand the wax must be manufactured at a reasonable cost 

 and yet conform to the requirements as to melting point and size of 

 pieces. This matter has required constant attention but may now be 

 placed on a more satisfactory basis when industry has returned to 

 conditions of peace. 



The bakers have experienced heavy losses and have required special 

 attention and methods. Education in matters of cleanliness and a 

 reform in some matters of handling flour have yielded good results. 

 The exchange or refilling of used sacks has been found to be the source 

 of much trouble. Experiments have shown that when empty sacks are 

 placed in the oven, three or four deep on boards and left for five min- 

 utes, all the insects in them are killed at the usual temperature of 232° 

 C. While it is necessary to watch the sacks closely to prevent scorch- 

 ing, this practice has given great relief. All rye proofing boxes and 

 other utensils have likewise been heated in the oven with a result that 

 ibadly infested bakeries have been entirely freed from insects. 



The study of the relative susceptibility of the various flours and 



