August, '14] GOODWIN: HEAT COXTROL FOR MILL INSECTS 315 



paper saturated wath water, thus completely preventing condensation 

 when making moist-atmosphere tests, and insuring a very humid 

 atmosphere. In dry tests this was removed. An atomizer throwing 

 hot water, was used without success, as was also small amounts of live 

 steam. The special burner "was modified so that small amounts of gas 

 could Tae used with a low flame and consequently the rise in temper- 

 ature in the oven was necessarily extremely even and slow. The gas 

 pressure proved to be too strong and a pressure reducer was therefore 

 devised to reduce the gas pressure from eight ounces to one-half ounce. 

 A good grade of machine oil was substituted for the water which is 

 ordinarily used in such a pressure reducer. The regulator was adjusted 

 until the pressure was sufficiently reduced to require no further atten- 

 tion as the machine oil does not evaporate. A large Mithoff hygrom- 

 eter, reading direct, was used to register the percentage of moisture 

 present. These readings were checked by the use of a wet and dry 

 bulb thermometer and the results were calculated from the psychro- 

 metric tables of the United States Weather Bureau. A wet bulb 

 thermometer will not register the minimum temperature correctly, 

 unless the air is circulated around it. To obtain this circulation some 

 device that will circulate the air around the wet bulb thermometer is 

 required. An electric bell was modified for this purpose by removing 

 the ball from the vibrator arm and replacing it with a small fan made 

 from light, soft wood. This modified electric bell was operated with 

 two dry batteries, and the rapid vibration of the fan blade circulated 

 the air around the base of the thermometer. 



The following list of species were used in these experiments: — 



Silvanus surinamensis L. Sitodrepa punicea L. 



Cathartus advena Walt. Triboliurn confusimi Duv. 



Cathartus gemellalus Duv. Tenebrio molitor L. 



Lcemophloeus minutus Oliv. Plodia interpuncteUa Dubn. 



Trogoderma ornatum Say. Ephestia kuehniella Zell. 



Attagenus piceus Oliv. * Calandra oryza L. 



Tenebrioides mauritanicus L. 



In the oven experiments most of the different species of insects 

 succumbed at a slightly lower temperature when using moist heat than 

 when using dry. The rice weevil (C. oryza) seemed to be especially 

 susceptible to heat in a moist atmosphere, repeated tests showing 

 that 3° C. to 4° C. less are required to prove fatal than when using dry 

 air. Several of the other species died at practically a uniform tem- 

 perature, regardless of the presence or lack of moisture. Consider- 

 able variation in the moisture content of infested material and in the 

 activity of the insects infesting the same was also experienced. In 

 the tests, most of the insects became very active at 40° C. to 43° C, 

 especially the adults. This activity increased with the increase in 



