Arachnida. 83 



As a rule the abdomen is darker than the cephalothorax, and 

 many species have the former red-brown and the latter black. 



The legs, usually, take the colour of the cephalothorax, and are, 

 hence, generally lighter than the abdomen, but to this there are 

 exceptions. Where the individual legs differ in colour, the two first 

 pairs are the darkest, and the dark hue corresponds in tint with the 

 dark markings on the cephalothorax. The joints of the legs are in 

 many species emphasized with dark colour, which is often repeated 

 in bands along the limb. 



The most remarkable point is, however, the pattern on the 

 abdomen, which, though varied in all possible ways, always 

 preserves a general character, so that we might speak with pro- 

 priety of a spider-back pattern. This pattern is fairly well 

 illustrated in the genus Lycosa, but is seen to perfection, and in its 

 simplest form in Segestria senoculata, Plate VIII., Fig. 1, and in 

 Sparassus smaragdulus, Plate VIII., Fig. 2. 



This peculiar pattern is so like the dorsal-vessel that lies just 

 beneath, that it is difficult to avoid the conclusion that we have here 

 an actual case of the influence of internal organs on the integument, 

 and this we believe to be the case. No matter how curious the 

 abdominal markings may seem to be, they never so far depart from 

 this fundamental pattern as to appear independent of it. 



Thus, in the genus Lycosa, which is by no means the best for the 

 purpose, but is chosen as illustrating Gegenbaur's diagram, PI. VIII., 

 we have the dorsal-vessel well marked in L. piscatoria, Plate VIII., Fig. 

 3, from which may be developed the other forms. In L. andrenivora 

 Plate VIII., Fig. 4, the male shows the vessel-mark attenuated pos- 

 teriorly ; and in the female, Fig. 5, the hinder part has become 

 broken up into detached marks, still preserving the original shape, 

 while the upper part remains practically unchanged. In L. allodroma 

 the disintegration of the mark has further advanced, for in the male, 

 Fig. 6, the upper portion has lost something of its shape, and the 

 lower part is a series of isolated segments. This process is carried 

 still further in the female, Fig. 8, where the upper portion is 

 simplified, and the lower almost gone. In L. campestris, Fig. 10, the 

 mark is reduced to a stripe, corresponding with the upper part of the 

 vessel-mark only : and, lastly, in the male L. agretyca, Fig. 7, this 

 upper part is represented by two spots, though even here traces of 

 the original form can be seen. 



A simplification of marking of another sort is seen in L. rapax, 



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