230 



STANLEY HIRST ON 



least as far as the fourth leg ; anteriorly each tube extends far 

 forwards, being coiled in a complicated manner near the second 

 leg, and there is another little coil near the first leg ; apparently 

 the orifice is somewhere above this limb. The author has not 

 been able to see tracheal tubes in any other Sarcoptid mites, 



Fig. 1. 



although an extensive series has been examined. This may be 

 due to the fact that the tracheal tubes are very fine and difiicult 

 to see unless filled with air. On the other hand, it is possible that 

 the mites of this family may have descended from ancestral forms 

 in which a tracheal respiratory system was present, but which 

 has disappeared in all the genera except Otodectes. 



In the Listrophoridae tracheal tubes are present in Chirodis- 

 coides caviae mihi and also in an undescribed Listrophorid mite 



