144 



GENERAL ZOOLOGY 



a skin disease of man commonly called "the itch." Other 

 species attack various mammals. Mange, a common skin 

 disease of dogs, is produced by mites burrowing in the skin. 

 Scorpions. The scorpions have the body plainly seg- 

 mented. In the common scorpion {Bu'thus, Fig. 82), found 



under sticks in our Southern 

 states, the pedipalps are greatly 

 elongated, making a formidable- 

 looking pair of claws. The ab- 

 domen is provided with a sting 

 at its extremity. This is not 

 operated like the sting of a bee 

 or wasp but is a lance-like organ 

 which is thrust into the enemy 

 by the whip-like motion of the 

 whole tail. The whip scorpion 

 (Thelyph' 'onus) , also found in 

 similar situations in the South, 

 is another formidable-looking 

 creature, with immensely de- 

 veloped pedipalps. These are 

 used to pull open decaying 

 wood in search of small insects, 

 which form its food. Its appearance accounts for the 

 dread it inspires, but there is no evidence to show that 

 it is harmful to man. 



Definition of Arachnida. The name "Arach'nida" is ap- 

 plied to the spiders, scorpions, mites, and ticks, all of which 

 are segmented animals with jointed appendages but lack- 

 ing antennae. There are normally four pairs of legs, though 

 the young stages commonly have but three pairs. The lack 

 of antenna? and the greater number of legs are the two 

 most conspicuous points of difference between the Arach- 

 nida and Hexapoda. 



Fig. 82. Photograph of scorpion 



American Museum of Natural 

 History 



