514 The Animal Kingdom 



The whip scorpions (order Pedipalpi) although large like the scor- 

 pions are quite distinctive in appearance. Their heavy pedipalps do not 

 end in pincers as do those of the scorpions but have numerous heavy 

 spines used for grasping prey. The first pair of legs is elongated into 

 slender tactile organs. There are two distinctive groups : the members 

 of one have a long caudal appendage while those of the other have 

 shorter abdomens and lack the tail. Those forms with the long tails are 

 commonly called vinegeroons due to the presence of glands at the base 

 of the tail which emit an odor like that of acetic acid. This large animal 

 (some 3 inches in length) is greatly feared by the uninformed, but is 

 actually totally harmless inasmuch as it has no poison glands. The 

 tailless whip scorpions are quite flattened and are usually found under 

 rocks and in caves. Several species occur in the southern United States. 



The ivind scorpions or siin spiders (order Solpugida) are rather 

 formidable appearing, though harmless, animals. They are distinguished 

 by their enlarged chelicerae and their hairy elongate legs. They run 

 rapidly, hence the name "wind scorpions." They hide under stones 

 during the day and search for prey during the night. The chelicerae are 

 used to grasp and tear their prey which consists of smaller arthropods. 

 They are abundant in the arid regions of the southwest but also occur 

 in the northern and western states. 



The daddy longlegs or harvestmen (order Opiliones) are familiar 

 forms which become particularly abundant during the fall of the year 

 in the northern states. The cephalothorax and abdomen are immoveably 

 fused. The most abundant harvestmen are the forms with the 

 small bodies and tremendously elongate slender legs. In the southern 

 United States and in the tropics, other members of the order have 

 shortened legs and often have bizarrely spined and colored bodies. They 

 are omniverous in their habits and often become tremendously abundant. 



The mites and ticks (order Acarina) are small rounded forms with 

 shortened legs. These are the most numerous of all the arachnid groups 

 in numbers of individuals. Many are free-living, others are parasitic, 

 and some live on plant juices. Due to their abundance and varied habits, 

 they constitute the most economically important group of the arachnids. 

 The cephalothorax and abdomen are fused as in the opiliones, but the 

 segmentation of the abdomen is obscured. Numerous species are free- 

 living in the leaf mold and feed on smaller organisms or on plant ma- 

 terials. The parasitic forms are found in a great number of places in- 

 cluding the hair follicles of mammals and the tracheal tubes of bees. 

 Many are important as transmitters of diseases such as tsutsugamushi 



