Spiders and Their Near Relatives 



Arachnida. The so-called abdomen of mites includes the true 

 abdomen and the last two thoracic segments; this is indicated 

 by the fact that it bears the third and fourth pairs of legs. 



In many mites the body is marked by numerous transverse, 

 fine lines, which are so impressed as to appear like the divisions 

 between minute segments, but the number of these divisions 

 on the ventral aspect of the body may differ greatly from that of 

 the dorsal. 



Normally there are six pairs of appendages, as with other 

 arachnids; these are the chelicerae, the pedipalps, and four pairs 

 of legs. 



As a rule the chelicerae consist of two segments and are often 

 chelate. In many forms, however, the chelicerae are slender, 



Fig. 62. SEVERAL TYPES OF PEDIPALPS 

 a, Bdella b, Cheylctus c, Arrenurus d, Trombidium (adapted from Banks) 



needle-like, and fitted for piercing. This difference in form of 

 the chelicerae is not of great taxonomic value, as in several cases 

 the two types exist within the same family. 



The pedipalps consist of not more than five segments; the\ 

 may be prominent or greatly reduced in size. They vary greatly 

 in form and in function. In some mites, they are simple, filiform, 

 and have a tactile function; in others they are specialized fo ; 

 predatory purposes, being armed with spines, hooks, or claws; and 

 in still others they are chelate, the chela being used for clinging 

 to some object. In some forms, more or less distinct endites are 

 present. In the harvest-mites, and in some other families, the 

 next to the last segment of the pedipalp is armed with one or two 



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