22 Acarology 



may become terminal rather than lateral in position. The movable 

 digit may become long and threadlike as it is in the spider mites. 

 In the ticks the chelicerae are chelate but the movable digit is lateral 

 rather than ventral and the teeth are on the outer surface of the chelae, 

 not on the inner. The chelicerae of the ticks function as anchors and 

 their structure is well adapted for this purpose (Figure 19). 



Special sense organs and setae are found on the chelicerae of many 

 mites. At the base of the movable digit in some mesostigmatids an 



Figure 16 The chelicera of Para- 

 situs fucorum (DeGeer), 1778. 

 (After Vitzthum 1940) 



The chelicera of the 

 male of Heterozercon audax Ber- 

 lese, 1910. (After Vitzthum 1940) 



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Figure 18 The chelicera of Der- 

 manyssus gallinae (DeGeer), 1778. 



Figure 19 The chelicerae of Ixodes reduvius (Linnaeus), 1758. Left, dorsal 

 and ventral views of the male; right, dorsal and ventral views of the female. 

 (After Vitzthum 1940) 



