TWO SPECIES OF PARASITIC MITES. 339 



that of Sarcoptes scabiei. except that the wrinkles are much fewer 

 and finer. At the anterior end of the body the organs of manducation 

 are grouped together into the form of a sub-quadrate rostrum, which 

 projects considerably beyond the front of the cephalo-thorax, though 

 it is, to a certain extent, retractile under it. The rostrum, seen from 

 the dorsal surface, is somewhat rectangular in outline, the outer 

 angles being slightly rounded off and the line of the front curved 

 outwards to a certain extent. Its length is considerably greater 

 than its breadth, being on an average about 0.025 mm. broad and 

 0.015 mm. long. It is composed essentially of the following parts,* 

 viz. : (1) A long delicate lingua, or tongue, which, however, is very 

 difficult to discern clearly until the animal has been submitted to 

 strong pressure, when it sometimes may be seen as a stout bristle 

 projecting beyond the anterior margin. (2) A pair of long, acutely 

 conical unjointed mandibles running parallel and close together during 

 the greater part of their length, and apparently forming a sheath for 

 the median tongue. ( 3) A pair of maxillae firmly united at their base, 

 but bearing at their outer and anterior angles a pair of two jointed 

 palps, one on each side of the mandible, the first joint being large 

 and sub-rectangular, the second small and conical. Towards the 

 side from the insertion of the palp, the angle of the maxilla is 

 extended into a short spine. With the exception of the characters 

 which we have just enumerated, namely, those of the skin and of 

 the rostrum, and perhaps also those of fie digestive canal, which 

 however we have not been able to make out, the male and female 

 present an entirely different appearance, and it will be most con- 

 venient to consider them separately. 



In the male, which as stated above is flattened from above down- 

 wards, the legs arise on the ventral surface a short distance in from 

 the lateral mai'gin, so that the first and part of the second joints are 

 hidden from view when looked at from above. The number of 

 joints pi-esent in each of the legs is four, the second probably corres- 

 ponding to the second and third in Myobia musculi, and other closely 

 allied species. They are all strengthened by very light brown rings 

 of chit-in which encircle them and form points of attachment for the 

 flexor muscles. The first joint in all the eight legs is somewhat 

 triangular in outline, the base of the triangle, which is the side 

 nearest the middle line of the body, being somewhat incurved, with 

 the angles adjacent to it slightly rounded, the anterior angle running 

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