No. 104.] 115 



Upon critical examination they were found to be identical with 

 the common cheese-mite, Tjrofjbjphus siro (Linn.) — a species 

 wliich, 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 Linnjeus, 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 some in- 

 dividual features presented in some examples, it was named and 

 figured by De Geer (vol. 7, pi. 5, fig. 15) as Aca/'iis dojiiestieiis^ 

 when he had found it occurring in meal, sugar, and smoked meats. 



This insect had not been previously known as infesting meats in 

 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, forming a layer 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 {A?ner{ca?i JVatiiralist, 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. Piley, he identified an exam- 

 ple 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 Roquefort 

 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 Aoariis 

 horrldus, 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, of the source of 

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

 might be pertinent to the question. The following communication 

 was returned : 



Replying to yours of the lOtli of June, we would state that the hams in ques- 

 tion are cured in the western part of Ohio, and in a brine made of salt, saltpetre, 

 and sweetened either with sugar or syrup. They are packed fresh from the ani- 

 mal in tierces, the brine poured in and the package closed — the meat being then 

 left to cure, a process requiring from forty to sixty days, although they are left 

 in this condition from one to twelve months. They come east in that shape and 

 are here taken out of pickle as they are wanted, and smoked. The dipping of 

 which you inquire, is never done to packed hams, but only to bagged or canvassed 

 hams; and is done that the coating may protect them from the deposit of eggs by 

 flies. The smoking that we gave them was not to exterminate the pest, but to 

 prepare them for market. It had, however, no effect upon the insect except 

 to make it more easily discernible. The attack seems to be increasing rapidly 

 through germination or some other process. 



