CHEESE MITES, ETC. 265 



CASE Acarids which live also in collections. Upon the insects them- 



XIV. 



selves, and devouring the excrements and the remains of the 

 Tyroglyphus, M. Ferris has found, at Mont-de-Marsan, the larvae 

 of the Cecidomyia entomophila. The walk of the Tyroglyphus 

 entomophagus is slow. It walks with the head bent down, in 

 such a way as to allow the ridge of contact of the two mandibles 

 which go beyond the hairs of the nape of the neck to be seen in 

 front. The males are as numerous as the females and a little 

 more agile. 



It remains to say a few words as to the best means of keeping 

 these mites out of collections, and of getting rid of them when 

 they have once effected an entrance. The insects which are most 

 liable to be attacked by the Tyroglyphus entomophagus are, as 

 already said, those which have not been well dried, or which have 

 been placed in ill-fitting boxes in a damp room. 



When the Tyroglyphus has attacked an insect, one perceives 

 outside little whitish points on the bodies of those with smooth 

 teguments, or on another kind a sort of greyish white powder 

 mingled in the hairs of cottony or downy kinds. Soon under the 

 insect invaded, or on the corresponding sides of the box, one 

 notices a matter of a greyish pulverulent aspect, recalling the 

 efflorescence of saline matters not deliquescent. This dust is said 

 to be quite different from the organic pulverulent de^bris which 

 results from the ravages of the Anthfenus or Dermestes; these 

 latter produce a fine sawdust, blackish or brownish, but dry and 

 non-adherent. Collections in the south of France, exposed to 

 damp, are very rapidly attacked by Tyroglyphus entomophagus. 

 The mouldmess which shows itself in a collection makes one 

 suspicious of mites, for mould and mites almost always go 

 together. 



When an insect is known to be attacked by Tyroglyphus it is 

 best to isolate it in a very dry box. If the insect is glossy the 

 mites which have got into it should be removed with a fine camel 

 hair brush. If the insect is scarcely attacked, it can be replaced on 



