Nellie B. Eales 33 



and it was often very difficult to find them. By keeping the cells 

 in the dark, however, the mites appeared to thrive better and were 

 more easily found when the cells were examined from day to day. 

 It follows from this that mite attack is worse in a dark cheese room 

 than in a light one, and the practice of having cheese rooms partly 

 or entirely under-ground is favourable to the mites, although necessary 

 in order to maintain an even temperature. 



Their fondness for darkness, however, is excelled by their love of 

 cracks, crevices and corners. They creep into cracks in the cheese 

 boards and shelves, and soap and boiling water will not kill them. 

 It is, in fact, extremely difficult to kill the adult mite and almost im- 

 possible to kill the egg. These mites have no breathing organs, but 

 breathe through the thin cuticle, so that it is far more difficult to kill 

 them by suffocation or fumigation than it would be if they possessed 

 breathing tubes like those of insects. The methods employed in the 

 dairies for keeping them in check are therefore often only waste of good 

 material. Some cheese makers, for example, dip the cheese in formalin, 

 believing that the formalin will kill the mites. Mites have been kept 

 immersed in 5 % formalin for over a tveek and at the end of that time, 

 though some had died, many were still active! The formalin washes 

 off the surface mites, but kills none of them. A very large number of 

 substances were experimented with, but only two were found which 

 killed the mites within a short time. These were Carbolic acid and 

 Carbon bi-sulphide. Carbolic acid, being poisonous, cannot be used 

 on the cheeses themselves, but it might be used for scrubbing the shelves, 

 and especially the corners. A 5 % solution killed the mites in two 

 minutes ; increasing the strength did not cause their death any sooner 

 than this. Fovir 10 lb. Stiltons were removed to an unused room, 

 freed from mites and kept free by the use of Carbon bi-sulphide. This 

 substance is a heavy, yellow and evil-smelling liquid which vaporises 

 very readily and which leaves behind neither smell nor taste. It is 

 used on flour, grain and many other food stuffs and destroys all forms 

 of animal life. It is not harmful when breathed in small quantities 

 by human beings, but is highly inflammable and should not be brought 

 near a light. The vapour of the bi-sulphide kills the mites almost in- 

 stantaneously, but although it is a heavy gas, the vapour does not work 

 underneath the cheeses, neither does it kill the eggs. The bi-sulphide 

 was used in several ways until the most satisfactory was found. 

 (1) The cheese was covered with a bell jar and a shallow vessel con- 

 taining the bi-sulphide was stood on an inverted gas jar placed inside 



Ann. Biol, iv 3 



