292 For tt- second Report on tee State Museum. [150] 



them. No attack of the kind had previously come under the observa- 

 tion of Mr. Wessels, .or of those engaged in the same trade with whom 

 he had conferred. 



Upon critical examination they were found to be identical with the 

 common cheese-mite, Tyroglyphus siro (Linn.), a species which, 

 although frequently occurring in vast numbers in cheese, has long 

 been known to thrive equally well on several other 

 articles of food. It is not at all uncommon in 

 flour, and when observed therein by Linnaeus, he 

 presumed it to be a distinct species, and named 

 it Acarus farince. When the same insect came 

 under his notice in milk, it was designated by him 

 as Acarus lactis. From unusual features presented 

 in some examples, it was named and figured by 

 De Geer (vol. 7, pi. 5, fig. 15) as Acarus domesticus, 

 when he had found it occurring in meal, sugar, 

 and smoked meats. 



Fig. 49. — The cheese- ^nrs insect had not been previously known as 

 mite, Tyroglyphus siko . . - . , o. i 



— enlarged. infesting meats m this country,* although a closely 



allied species, Tyroglyphus longior Gervais, as identified by Professor 



Riley, had been found in a pork-packing house in a western city, 



in such abundance as to form layers of half an inch thick in places, 



beneath sacks of fertilizing material piled upon the floor, composed' 



of livers, lungs, and kidneys, after they had been cooked and dried by 



steam {American Naturalist, xvi, 1882, p. 599). This latter species is 



distinguishable from the cheese-mite (according to Murray) by its 



more rapid movements, larger size, longer and more cylindrical body, 



and more shining hairs sticking out on every side. The habits of the 



two are said to be much the same, and it is of interest that in a small 



bit of the infested ham received by me that was sent to Prof. Riley, 



he identified an example of T. longior associated with T. siro. The two 



have been also found in association on old cheese, but T. longior in by 



far the smaller proportion — in but eight per cent upon some Rochefort 



cheese, and only one per cent on Septmoncal. It is this species which, 



about half a century ago, enjoyed for a time the notoriety of having 



been brought into being as a human creation through the electrical 



experiments of Mr. Cross, named at the time as Acarus horridus, before 



its identity with T. longior had been ascertained. 



As the origin of the mites occurring upon the ham could not be 



readily answered, inquiry was made of Mr. Wessels as to the source of 



the meat, its method of curing, and for any other information that 



* See subsequent notice of the same insect infesting smoked meats in Everett, Pa., 

 in FortiethlRept. N. Y. St. Mus. N. H. for 1886. p. 130. 



