TRAGARDH, MORPHOLOGY AND PHYLOGENY OF PARASITIDiE. 



Position of the grenital aperture. 



As is well known, the Parasitidce are generally divided 

 by the systematists into two groups, according to the geni- 

 tal aperture being situated in front of, or surrounded b}^ 

 the sternal shield. The question as to which position is the 

 more primitive has, however, been variously answered.^ 

 OuDEMANS, when comparing the Prostigmata with the Meso- 

 stigmata [9. p. 94 — 95] says >>I consider the Prostigmata 



1^1% 



/ 



\.-:- 



<^^ 



å 



Fig. 11. 



Ficr. 12. 



Fig. 11. Gamasiphis loricatus Tijdh. cT, X 50, ventral view 



(after Trägårdh). 



Fig. 12. Dinyehus tetraphyllus Berl. cT, X 120, ventral view 



(after Trägårdh). 



younger than the Mesostigmata Yet a few primitive 



characters have persisted, e. g. the situation of the genital 

 openings behind the 4th pair of legs.» 



The consequence of this would seem to be that even in 

 the Parasitidce he regarded those genera the more primitive, 



^ I omit here the discussion regarding the original position of the 

 genital aperture in the Acarina, as this is exhaustivelv treated bv Reuter 

 [12. p. 35-38]. 



