ACARI 597 



The latter circumstance of there being sexual différences 

 in the shape of the hypostomatic hairs is of spécial interest. 

 Until 1910, the opinion prevailed amongst acarologists that the 

 sexes exhibited no différence with regard to the hypostoma. 

 The author then proved that in the gen. Dinychus there was 

 a distinct différence in this respect (1910, p. 454-455). 



The gen. Dinychus occupies, however, a soniewhat isolated 

 position amongst the Uropodinae, and it was impossible to say 

 whether the feature was more common in the Uropodinae, 

 or whether Dinychus was an exception. 



The discovery of similar, but still more marked, sexual 

 différences in Urodinychus Kramerii (G. Can.) renders it, however, 

 highly probable that this feature will, on further research, prove 

 to be very common in the Uropodinae, and the reason why 

 it has hitherto been overlooked is the almost completely con- 

 cealed position of the gnathosoma above coxael, which 

 makes dissection extremely difïicult. 



The shape of the maie differs from that of the female 

 (fig. 120) in being less broadly rounded anteriorly, and poste- 

 riorly.The marginal shieldisfused with the central shield 

 at the anterior end, on a level with the base of the mucro, which 

 is set ofî from the « shoulders » by a slight sinuosity. 



Marginal shield of even width throughout, divided by 

 transverse, radiating, light-coloured Unes into small square 

 plates (fig. 122). The Hnes do not, however, reach the margin 

 of the shield, but only extend from the inner margin a httle 

 beyond the middle ; consequently, the band of square plates 

 is surrounded by another undivided band. The latter bears a 

 row of numerous small hairs placed at regular intervais, as a 

 rule each corresponding to one of the small plates, and pointing 

 straight outwards. 



The centralshield bears numerous small hairs ail over, 

 and is highly arched, but without any ridges or dépressions ; 

 at the anterior end it slopes downwards considerably and ends 

 with a very thin edge in which a pair of hairs is inserted. 



