SOME INSECTS AFFECTING CHEESE, HAMS, FRUIT, ETC. 101 



Aristotle knew the cheese mites and spoke of them as the smallest 

 of living creatures. Many subsequent writers have figured them and 

 mentioned them, but the full life history was not known until 1868, 

 when Claparede determined that the genus Hypopus was composed of 

 forms which are steps in the development of true tyroglyphids. 



All through the summer months, and i:i warm houses during the 

 winter months, these creatures breed with astonishing rapidity and 

 fecundity. The rapidity of multiplication and the extraordinary num- 

 bers in which these mites will occur under favorable conditions are 

 almost incredible. In 1882 T. longior was found in an Ohio packing 

 house, covering the dried and packed refuse (ready for sale as a fertil- 

 izer) in a layer which in some places was half an inch in thickness. At 

 a low estimate 1 square inch of such a layer would contain 100,000 indi- 

 viduals. The females bring forth their young alive, and these in turn 

 reach full growth and reproduce, until a 

 cheese, once infested by a few, swarms with 

 the crawling multitude, which cause its solid 

 mass to crumble and become mixed with 

 excremental pellets and cast-off skins. 

 Through the summer months the mites are 

 soft bodied and have comparatively feeble 

 powers of locomotion, and when they have 

 become numerous enough to devour the 

 whole of a cheese, with no other food at 

 hand, it was for a long time a puzzle to know 

 what became of them and to understand 

 how a cheese could become affected without 

 contact with another infested cheese or 

 without being placed in an infested room. It 

 has been ascertained, however, that when 

 necessity requires it, and when the insects 

 happen to be in the proper stage of growth, 

 they have the power of not only almost indefinitely prolonging exist- 

 ence, but of undergoing a complete change of form, acquiring hard, 

 brown protective coverings into which all of the legs can be drawn in 

 repose. Back in Van Leeuwenhoek's time this Dutch naturalist showed 

 that even the softer form can undergo a fast of eleven weeks without 

 apparent discomfort, and it is now known that in the hard-shell or 

 Hypopns state it may remain for many months without food. 



In the majority of cases, however, where a given cheese is completely 

 destroyed, all of the young and old mites perish and only those of 

 middle age which are ready to take on the Hypopus condition survive. 

 These fortunate survivors, possessing their souls with patience, retire 

 into their shells and fast and wait, and as everything comes to him who 

 waits, some lucky day a mouse or house fly or some other insect conies 

 that way, and the little mite clings to it and is carried away to some 



Fig. 47. — Tyroylyphus siro; female- 

 greatly enlarged (after Berlese). 



