ACARUS OF THE GENUS MYOB1A. 6 



Myobia, which evidently struck Claparede as being one of the 

 strangest creatures that he had met with. 



There certainly are two or three points about Myobia which are 

 very curious, and justify the Swiss naturalist's astonishment. The 

 first of these is that the genital openings in both sexes are on the 

 dorsal surface, both on slight elevations, that of the female not 

 being very far from the posterior margin, while in the male the 

 intromittant organ emerges in the median line of the back between 

 the second and third pairs of legs, an arrangement extremely un- 

 usual in nature, although it occurs in some few other Acarina. 

 The next point that strikes the observer is the exceptional form of 

 the tarsi and claws of the first pair of legs. Myobia lives upon 

 hairy mammals, and the front tarsi and claws are developed into 

 broad scoop-like organs, each with a curved hook projecting from 

 it, the whole forming a most efficient apparatus for holding on to 

 the hairs of the host. 



The third matter which is rather exceptional is that the claws of 

 the second, third, and fourth pairs of legs, although didactyle, are 

 unequal (on each leg). Of course, a tridactyle claw with the 

 central unguis different from the lateral ones is common enough, 

 but a didactyle claw with the two ungues unequal is somewhat 

 rare. 



As before stated, the Myobia hitherto known was supposed by its 

 discoverer, and most subsequent naturalists, to be a parasite of the 

 mouse only, although it did not appear to be confined to any par- 

 ticular species of mouse, being found both on field-mice and house- 

 mice, perhaps most abundantly on old specimens of the latter. 

 During the last two or three years, however, a Myobia has been 

 found upon the mole, which does not appear to differ from that of 

 the mouse in any respect except its somewhat greater size ; and no 

 acarologist has as yet ventured to make two species of them, so 

 that Myobia musculi still remains the sole representative of the 

 genus. 



The finding of a species of Myobia on the bat is not wholly devoid 

 of a certain quaint interest, when we remember that the early 

 zoologists looked on the bats as a link between birds and quadru- 

 peds, and that Linnams classed them amongst the Primates ; 

 while, on the other hand, the popular instinct in most languages has 

 usually associated them with mice, whence came such names as 

 " Rere-mouse " (from the Anglo-Saxon " rau-an," to raise or rear 



