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Stilton and Cheddar. These mites tlirive equally well in flour, stored 

 grain, dried fruits, drugs, hay, etc., when these are allowed to become 

 damp. The life-histories of all these species are similar, occupying 

 about four or five weeks. The eggs hatch in about 10-12 days after 

 being laid ; the larva feeds actively for about a week, then becomes 

 quiescent and moults, emerging as the first nymph. Three successive 

 moults occur before the adult appears. T. longior has an additional stage 

 after the first nymph stage ; in this form, known as the hypopus stage, 

 it attaches itself to other mites, flies or moths, and sometimes to the 

 skin and clothes of human beings. It is thus carried about until it 

 finds a suitable place, where it drops off, moults to the second nymphal 

 stage and commences feeding. Investigations have been made into 

 the manner of infestation of new cheeses. Stiltons are usuaUy made 

 from April to September and are cleared out of the dairies by December. 

 From December to April the Stilton room is generally empty or is used 

 for other cheeses that are not attacked by mites. Scrapings from 

 corners, window-ledges and shelves of such rooms invariably revealed 

 a few living mites among the dead individuals and dust, even in 

 dairies where the greatest precautions are taken. Only adult forms 

 were found, indicating that the mites pass the interval between the 

 Stilton periods in that stage. Experiments to determine the method 

 of dispersal from cheese to cheese and from shelf to shelf showed that 

 flies and moths can carry the mites, and this seems to be the most 

 probable method of dissemination, though other possibihties are that 

 the mites could be blown by a draught across the small space inter- 

 vening or that the person who turned the cheeses regularly may have 

 carried them in spite of every care and attention. Although these 

 pests have no eyes, they can distinguish between hght and darkness 

 and prefer the latter. For this reason attacks by mites are worse 

 in a dark room, and the practice of having cheese rooms partly or 

 entirely underground, while necessary in order to maintain an even 

 temperature, is favourable to the mites. 



It is extremely difficult to kill the adult mites and almost impossible 

 to kill the eggs. Soap and boiling water will not kill them on the shelves, 

 as they hide in cracks and crevices in the wood. Some cheese-makers 

 dip their cheeses in formaUn, but mites kept in 5 per cent, formalin for 

 over a week were alive at the end of that time. The only two sub- 

 stances that were found to kill the mites within a short time were 

 carbolic acid and carbon bisulphide. The former, being poisonous, 

 cannot be used on the cheeses themselves, but might be used for 

 scrubbing the shelves, at 5 per cent, strength. The vapour of carbon 

 bisulphide kills the mites almost instantaneously. The best method 

 of apphcation proved to be covering the cheese with a bell jar, the 

 bisulphide being allowed to evaporate in a small vessel at the top of 

 the jar. Even then a few mites still survive underneath the cheese. 

 The most effectual method was to paint the whole surface of the cheese 

 with carbon bisulphide, but this is a slow process and is costly. The 

 cheese must be treated three times ; once to kill the adults, again 

 when the eggs have hatched to kill the larvae, and a third time to 

 ensure that all are destroyed. Further experiments with these methods 

 will be carried out. Preventive measures are naturally better than 

 cure, and an attempt will be made in a dairy to employ such thorough 

 methods of cleansing that no mites can survive. 



