THE EEPOET OF THE No. 36 



leaves the mill in as good condition as if it had never been in contact with them. 

 Suppose, however, one takes a sample oi" flour which is, to all appearance, in good 

 condition from the mill badly infested Avith these beetles, and places it in a 

 tightly closed tin, thus assuring that no beetles can obtain entrance for oviposition. 

 An examination of this tin, say in six months' time, will in all probability reveal 

 the presence of a large number of beetles. This is due to the fact that the beetle 

 lays its eggs in such places as the inside of spouts, and in elevator boots. Thus 

 the presence of the beetles results in the contamination of passing flour with eggs. 

 They measure about 1/00 inch in diameter and could never be detected in the flour. 



The owner of a badly infested mill rarely experiences any trouble with his 

 flour, since he stores it for a ver}- short time, and when it leaves his warehouse 

 it is, in so far as he knows, a perfectly clean consignment. Should this flour be 

 :5old for local consumption it will probably be sterilized by being baked before the 

 newly hatched larva? have attained a suflieient size to attract the attention of their 

 consumer. If, on the other hand, the flour is exported to some such warm climate 

 as that of the West Indies, the time which must elapse, together with the tempera- 

 tures at which it will be kept, before it arrives at its destination, offer every 

 opportunity for the completion of at least the greater part of the beetle's life 

 cycle. A further delay iii the consumption of this flour may allow the completion 

 of several generations, with the result that, the consignment becomes seriously 

 infested. Such conditions ma}^ not often occur, but prior to the general adoption 

 of control measures, complaints were more frequently made of infestations develop- 

 ing in consignments of exported flour. Hence, from a national point of view, 

 it is seen that mill |)ests Jiave a greater significance than merely in so far as they 

 affect the mil] in which they live and breed. 



Foi-tunately, we have at our disposal several means of reducing to a minimum, 

 if not in all cases entirely eradicating, these pests, and the majority of millers 

 have shown great energy and enterprise in adapting these remedies to their mills. 

 The most important control measures are: superheating, fumigating and freezing. 



Superheating is a method of control based upon the observation that a tem- 

 j)crature of about 120° Fah. will destroy any stage of insect life in a very short 

 time. A mill in which the pests are controlled by superheating is usually fitted 

 with sufficient permanent steam pipes to raise its " room temperature " to about 

 130°F., but similar results can be obtained with the aid of temporary coils, and 

 by utilizing the heat from a drier. 



Heating is most conveniently effected over a week-end. When the mill closes 

 down on Saturday night all elevator boots, etc., are opened up to allow a free 

 circulation of air, and the heat is turned on. By the following morning the 

 required temperature is obtained, and by preference it is maintained for over 

 twenty hours. This duration of time is not necessary for the destniction of ex- 

 posed pests, but it is desirable in order to assure that the heat penetrates into 

 all accessible places. Work can be resumed on the Monday, though the first part 

 of this day is usually occupied in giving the mill a thorough cleaning down. The 

 result of this treatment is that all species of mill pests, in whatever stage they were 

 ])resent. have tfcen desti'oyed in. every part of the mill which was raised to a tem- 

 perature of 120°, whether such places were accessible to a free circulation of air 

 or not. Superheating is becoming increasingly popular with millers, and it is 

 sip-ni (leant that only those who have never employed it are able to advance serious 

 iibj('cti'in> to its use. 



