Oribatid Mites taken in the neighbourhood of Cambridge. 427 



Exhibition of Oribatid Mites taken in the neighbourhood of 

 Cambridge. By C. Warburton, M.A., Christ's College, and 

 N. D. F. Pearce, M.A., Trinity College. 



[Read 29 February 1904.] 



The Oribatidae or Beetle-mites form a compact group of the 

 Order AcARl. They may be recognised by their strongly chitin- 

 ised integument, which gives to many of them a remarkably 

 beetle-like appearance, and more especially by the possession of 

 a pair of organs on the cephalothorax. These consist of crater- 

 like pits, from the centre of which proceed modified hairs of very 

 varying shape, and of unknown function. The pits are known as 

 pseudostigmata, and the hairs as pseudostigmatic organs. 



These mites are small creatures, averaging perhaps one-fiftieth 

 of an inch in length. They are vegetable feeders, living on such 

 materials as moss, lichen and rotten wood, and they are most 

 readily taken by shaking out over white paper moss or other 

 substance which has been collected in bags from likely localities. 

 Notwithstanding their small size their movements, as they slowly 

 crawl about, cause them to be easily detected by a practised eye. 



The Acari have received extremely little attention in this 

 country, and this is the first attempt to investigate the local 

 fauna of any acarine group. It is, perhaps, worth noting that in 

 four winter months specimens of forty-seven out of the hundred 

 known British species have been taken in the neighbourhood, and 

 that every one of the fifteen British genera is locally represented. 



ARACHNIDA. 



Order Acari. 

 Fam. Oribatidae. 

 Sub-fam. Pterogasterinae. 



Gen. Pelops, C. L. Koch. 



P. acromios, Hermann. 



P. fuliginosus, C. L. Koch. 



P. phaeonotus, C. L. Koch. 



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