20 AMERICAN SPIDERS 



aids in the transfer of the spermatophore to the female during 

 mating. However, the exact use of this unique structure has never 

 been observed. 



A single species of this curious rare group is known from 

 southern Texas. A few other species occur in tropical America 

 and in Africa, but the appearance of even a single example of this 

 order is an event. 



Whip Scorpions. The whip scorpions resemble the true scorpions 

 in a general way, but are readily distinguished by the absence of a 

 caudal sting and by important differences in the other appendages. 

 The pedipalpi are enlarged into formidable grasping organs, which 

 bear, along their inner edges, numerous teeth or sharp spines that 

 aid in crushing prey. The long, slender first pair of legs is special- 

 ized as organs of touch. 



The tailed whip scorpions have a slender, jointed, whiplike tail, 

 which is responsible for their common name. In this group the 

 carapace is longer than it is broad, the pedipalpi are very stout, and 

 the first pair of legs is of only moderate length. Essentially noc- 

 turnal in habit, these creatures spend the day in crevices in trees or 

 under objects on the ground, and are active burro wers into sand 

 and debris. Although greatly feared by uninformed peoples, the 

 whip scorpions are without poison glands and incapable of causing 

 more than slight mechanical injury with their clumsy, raptorial 

 pedipalps. At least some of them are known to emit an odor re- 

 sembling' acetic acid from glands located in the base of the tail, a 

 fact that finds expression in the name of "vinegaroon" given by 

 some Americans to Mastigoproctus giganteus (Plate VIII), the giant 

 whip scorpion, which often measures three inches long. 



The tailless whip scorpions are flattened creatures, which again 

 have the carapace longer than broad, but are without any trace of 

 a tail. The first pair of legs is modified into very long, lashlike 

 whips, the tips of which are flexible. These animals live in dark, 

 sheltered places, such as fissures in the rocks and under the bark 

 of trees. They frequently occur in great numbers in caves, and 

 many of them enter houses. They run with great speed when 

 disturbed. Two or three species occur in the southern part of the 

 United States. 



Micro-Whip Scorpions. As their common name suggests, these 

 tiny arachnids resemble the tailed whip scorpions, but they are far 



