DEVELOPMENT AND IMMATURE STAGES. 135 



error, and considering the general accuracy of Dr. 

 Nalepa's work, I should probably have been justified 

 in relying upon his statement without further observa- 

 tions of my own ; however, as he did not state his 

 methods of working out the life-history, I thought it 

 would be more satisfactory to check the result and to 

 see if it applied to other species also; moreover I 

 hoped to obtain some information as to the period 

 which the various stages lasted, etc., which might be 

 of interest. I think that I was not unsuccessful in this ; 

 but I may say at once that I found Nalepa's statement 

 of the two nymphal ecdyses to be correct, as might 

 have been anticipated, in the species which I in- 

 vestigated. 



My method of investigation was practically the same 

 as what I used for the OribatidaB, viz. I took an 

 ordinary glass microscopic slip 3x1 inch, and to the 

 middle of this I cemented with gold-size a glass ring 

 (section of tube) of a trifle less than one inch external 

 diameter ; the height of the ring, which constituted the 

 wall of the cell, was about one third to one half of an 

 inch. The gold-size was allowed to dry thoroughly 

 and all smell to go off. A piece of thick white 

 blotting-paper, a trifle less in diameter than the inside 

 of the cell, was then placed on the bottom of the cell 

 and slightly moistened ; upon this the Acarus, or Acari, 

 to be reared was placed with its food ; a second 3x1 

 inch glass slip, or a piece of one, was placed over the 

 top ; the edge of the glass ring having been ground 

 quite smooth ; the cover was fixed on by a clip, or a 

 thread wound several times round cell and cover; I 

 prefer the latter method. The food before being 

 placed in the cell must be carefully sterilised by being 

 baked or boiled, otherwise eggs and other Acari will 

 get in with it and render the observations unreliable. 

 The Acari do not usually like the baked or boiled food 

 as well as unsterilised food, but it is necessary to use 

 the former. Success depends greatly on maintaining 

 the precise hygrometric condition which suits the 



