284 ENTOMOLOGICAL SOCIETY 



from a pair of glands a preserving coating. Were this region 

 also expanded and the orifice removed from the capitulum, the 

 process of egg-laying would be seriously disturbed. 



The body in the mature state is provided with a number of 

 orifices : First, the respiratory system opens externally in the 

 stigmal plate, which is situated on each pleural side, behind and 

 a little^ above the coxas of the fourth pair of legs. The aperture 

 of the internal tracheal system is very minute and is situated upon 

 a little tubercle which varies in form in the different genera, and 

 is sometimes circular, sometimes elongate or comma-shaped. 

 This little tubercle is the perithreme and lies in a large, peculiar 

 cup- or disc-like, flat, or more or less concave plate which also 

 varies in the different genera in form and size and serves thus as 

 a very distinct criterium in classification. It is round or oval and 

 appears as if one corner of it had been turned over, but it has 

 always an elevated brim, and its surface appears to be punctured 

 by many minute perforations. It is generally coated by a white, 

 dry, membraneous exudation which covers the punctures in a 

 bubble or pearl-like manner. 



Another orifice of the body is that of the genital apparatus in 

 both sexes. As I have mentioned above, this aperture is situated 

 in the anterior region of the ventral surface and often very close 

 to the insertion of the capitulum. In other instances, and es 

 pecially in the free-living state, it is removed back to the space 

 between the fourth coxag. The external orifice of the female 

 genital organ forms a transversely-oval slit, surrounded by a 

 hardened ring which is particularly distinct in the anterior region. 

 The genital opening in the male is situated in about the same 

 position as the female, and forms here a transverse cleft, the 

 borders of which are slightly elevated or bulging. 



The third orifice is that of the anus. It represents a longitud 

 inally oval opening on the posterior half of the body and is fur 

 nished with two valvular lamellas on its side and is surrounded 

 also by an indurated ring. 



The Legs : The legs of the Ticks are ambulatory organs and 

 consequently strongly developed. The proportion of their length 

 is about i.ooo, 0.820, 0.935, 1.105, respectively. 



The legs are all six-jointed, including the immovable coxal 

 joints or plates. Some authors counted five joints, while others 



