ARTHROPODA. 253 



plants. The cattle- tick of the South is the means of 

 spreading the cattle disease known as Texas fever. The 

 mange among live stock, and itch in man are caused by 

 parasites belonging to this group. 



FIG. 98. Scorpion (Buthus}. Photo by Folsom. 



Questions on the Figure. Compare the scorpion with figures of 

 Crustacea, insects, and spiders, noting the chief differences and 

 likenesses. Of what tse is the long, segmented abdomen in the 

 scorpion? What are the nearest kin of the scorpion? 



Limulus, the king-crab or horse-shoe crab, is classed by some 

 zoologists near the spiders. In external appearance it is more like 

 the crabs, but its internal anatomy and its development suggest its 

 classification with the arachnida. 



