[73] 



Qn tbe palpi of ffresb^Mater /nbltes as m^s to 

 MstiUGUisbtng Sub=ffamiltes» 



By C. F. George, M.R.C.S., Lon., etc. 



ALL entomologists have observed the wonderful modifications 

 which occur in the same organ in different insects, and so 

 well is this known, that it has more than once formed the 

 basis of classification ; it is, however, unreasonable to suppose that 

 the examination of a single organ should be sufficient to enable the 

 most learned to identify any and every species not previously seen 

 by him. Nevertheless, when applied to small circles, this knowledge 

 of the variation of certain organs may be of the greatest use in 

 identifying "groups," even -though it entirely fails to distinguish 

 individuals. In studying the fresh-water mites, I have been struck 

 with the variation to be found in the palpus of each sub-family. 

 This organ only consists of five joints, and readily admits of ex- 

 amination under the microscope even whilst the creature is alive, 

 as, for the most part, it is alternately extended and flexed when the 

 mite is in confinement, in its endeavour to escape, and a very 

 cursory examination will frequently enable the observer to pro- 

 nounce at once, in which sub-family the creature is to be placed. 

 I thought, therefore, that a few sketches of the palpi, from speci- 

 mens found by myself, would be of interest to the readers of this 

 Journal, and more particularly to those who are members of the 

 "P. M.S.," in whose boxes I have placed specimens of these 

 mites, and intend, should circumstances permit, to continue to do 

 so, when my turn for changing slides shall come round. The fresh- 

 water mites are divided into three families : — 



1.— Flussmilben. 



2.— Weihermilben. 



3. — Sumpfmilben. 



It is the first family — Flussmilben — Hygrobatides, or river- 

 mites, — I intend to illustrate on this occasion ; perhaps at some 

 future time I may deal with the other families. 



Fig. 13 represents the palpus of the extremely curious mite 

 called Marica Musculus. Here there does not seem much to 



