70 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



than a fine or granular material, and that the element of flakiness is, so 

 far as choice is concerned, dominant over nutritive differences, if nutri- 

 tive differences exist. To check this, some bran was ground to fineness 

 and given an equal exposure to the beetles with the coarse bran. An 

 average of 60 per cent of the beetles were found in the coarse bran and 

 40 per cent in the fine bran. Again four sections of a jar were filled 

 with fine sawdust and the fifth with coarse sawdust. The sector with 

 the coarse sawdust contained an average of 43.3 per cent of the beetles 

 and the other sections averaged 15.3 per cent, 13.6 per cent, 12.2 per 

 cent and 14.6 per cent respectively. It may therefore be concluded 

 that the factor of coarseness is dominant and the factor of nutritive 

 choice, if measurable, is less significant. 



In the study of the relative development of the insects in the various 

 wheat flours and substitutes, it was found that the larval life might be 

 prolonged in certain wheat flour substitutes and that this prolongation 

 took place in the last larval instar. In soipe cases the life-cycle was 

 twice as long as in other cases. These experiments were all carried on 

 under the same conditions, in an atmosphere of 70 per cent of relative 

 humidity. (The temperature curve on the chart shows a drop of a 

 few degrees near the end of the experiment, with a consequent pro- 

 longation of some of the pupal stages.) Further experiments now 

 under way will furnish additional data on relative development. 



The data accumulated from examinations of flour in warehouses have 

 not yet reached the proportions which will give significant percentages, 

 but the above results combined with general experience make it seem 

 that coarseness is a factor in susceptibility. The fact that coarse 

 cereals cannot be bolted through fine cloths together with the choice of 

 the insects as shown in the invasion experiments substantiates this 

 contention. The factor of relative development must await further 

 investigations before its importance in influencing susceptibility can be 

 judged. 



Mr. T. J. Headlee: Were any chemical studies made t)f the 

 effect of heat on the flours, or feeds? 



Mr. W. a, Riley: There were a number of experiments carried 

 on, both by the chemists who were interested in the general effect on 

 proteids and also by ihe home economists of the department, showing 

 that there was no injury at this temperature. 



Vice-President W. C. O'Kane: The next paper will be pre- 

 sented by Mr. W. E. Britton. 



