262 ARACHNOIDEA. 



GASff myriads of angiiillul^ which often swarm there. It looks some- 

 times as if they darted their sharp mandibles into these creatures ; 

 but this is an illusion, and it is truly the vegetable cells that they 

 shear asunder with their scissors-like mandibles. These are shown 

 in the woodcut. 



The species is at once distinguishable by its rather rectangular 

 form and by the back being raised' in humps as shown in the 

 figures. 



It seems very probable that this species, described in 1873 by 

 M. Megnin, is the same as that noticed by Boisduval in 1867 \ but, 

 as the notice by the latter contains no description, it is impossible 

 to give the preference to his name even although it should turn 

 out that he meant the same species as M. Megnin. All that 

 Boisduval says of it is, that he had observed, when he had 

 descended into certain parts of the catacombs or in the quarries 

 occupied by mushroom growers, that the common mushroom 

 Agaricus edulis, was often invaded by an Acarus visible to the 

 naked eye, which covered the pedicule and spread itself even 

 between the folds of the pileus. It is, he adds, along with a small 

 brachelytrous beetle, which the mushroom growers call capuchin, 

 a scourge for this kind of culture. All the description he gives of 

 it is that it is roundish and of a feeble rusty grey colour. 



Rhizoglyphus mycophagus (Tyroglyphus mycophagus, Megnin, Journ. 

 Anat. Phys. 1874). 



This is another mushroom - feeding Acarid from which M, 

 Megnin obtained some of his more important facts regarding the 



