Spiders and Their Near Relatives 



thorax, the coxae of the appendages meet on the middle line 

 (Fig. 42) so that there are no traces of sternites except perhaps 

 the labium and a triangular plate between the last pair of legs 



which is visible in some genera. 



The median eyes are wanting; there 

 are only one or two pairs of lateral eyes; 

 and in some forms even these are wanting. 

 The beak is well-developed and con- 

 sists of a labrum and a labium; the former 

 is broad and extends down on each side of 

 the narrow labium. 



The chelicera? are complicated in struc- 

 ture, and as their variations in form afford 



VENTRAL^ASPECT OF C naracterS that are mUch USed in dassifica- 



cephalothorax and tion, they merit a detailed description. 

 of two abdominal Th are t wo-jointed and chelate; the 



SEGMENTS - J 



chela? are horizontal, the movable second 

 segment or finger forming the lateral mem- 

 ber of the pincers (Fig. 43). 



The movable finger of the chelicera bears on 

 its lateral side near the tip a spinneret; in some s. 

 forms this is simply a slight eminence on which 

 the ducts of the silk glands open (Fig. 44); 

 in others it is prolonged into a slender, more 

 or less branched stylet (Fig. 43); and in a 

 South American genus the finger of each 

 chelicera bears three simple spinnerets. The 

 elongated type of this organ is designated 

 by different writers as process of the finger, 

 as stylet, and as galea; but now that its 

 function is known, the term spinneret is sug- 

 gested as more descriptive and one which can 

 be applied to all types of the organ. 



The finger of the chelicera bears also on 

 its inner margin a comb-like organ, the 

 serrula; this is either attached throughout its 

 entire length to the finger (Fig. 43) or the distal part is free 

 (Fig. 44). Balzan (91) divided the order into two suborders 

 using these two types of the serrula as the distinguishing 

 characters. 



Fig. 43- CHELICERA 

 OF CHELIFER 

 s, spinneret more en- 

 larged /, flagellum 



40 



