24 Acarology 



In addition to the simple, leglike pedipalps there are several impor- 

 tant modifications. In some of the parasitic groups the pedipalps are 

 reduced to vestigial knobs with specialized spines or angular projec- 

 tions adapted to their parasitic habit. In the Trombidiformes the palpi 

 may become enlarged and function as accessory chelicerae. 



Figure 21 The last two segments of Figure 22 The pedipalp of a 



the pedipalps of Euschongastia indica cheyletid mite. 



(Hirst), 1915. 



In some of the Trombidiformes the relationship between the palpal 

 tarsus and palpal tibia is modified. The tibia is frequently provided 

 with a terminal stout claw which displaces the palpal tarsus to a ven- 

 tral position. A chelate pedipalp results from this displacement (Fig- 

 ure 21). In its unmodified form the chelate pedipalp serves as a hand. 

 The dorsal claw is opposed by the palpal tarsus or thumb and the mite 

 is capable of picking up and holding not only its food but other ob- 

 jects as well. 



In the Cheyletidae the chelate type of pedipalp is enormously de- 

 veloped (Figure 22). The tibia is provided with a stout claw and the 

 tarsus which has moved medially is also provided with cteniform or 

 falcate, clawlike setae. In this group the right and left pedipalps oppose 

 each other and form a powerful grasping organ with which to press the 

 prey against the relatively minute chelicerae. The pedipalps of the 

 Cunaxidae and Bdellidae function in a similar fashion but these lack 

 the palpal thumb. 



Legs: The majority of the Acarina possess three pairs of walking legs 

 in the larval stage and four pairs in all subsequent stages. The erio- 



