392 



ARTHROPODA 



glands. It is the 'sting' of the animal which causes painful wounds in 

 man, and in the large tropical species is, perhaps, fatal. Usually scorpions 

 feed upon insects, which they seize with the pincers and kill with the sting. 

 On the ventral surface of the second abdominal somite (fig. 421) are a 

 pair of appendages, the combs or pectines, rods with teeth on one side, of 

 uncertain function. They are clearly appendages with modified gill 

 leaves, and from their nearness to the sexual opening and their rich nerve 

 supply are supposed to be stimulating organs in copulation. The next 

 four segments bear spiracles which lead to four pairs of lung sacs. The 



FIG. 422. Thclyphomts caudatus. i, chelicera; 2, pedipalpi; 3, flagellate third leg; 

 4-6, walking feet. Below, chelicera enlarged. 



heart is abdominal and the liver diverticula are confined to the same 

 region. The large number of abdominal ganglia distinct from the 

 cesophageal ring is also characteristic. From three to six pairs of eyes 

 occur. 



The scorpions are inhabitants of warm regions, ranging north with us to the 

 Carolinas and Nebraska. Buthus,* Centrums* 



Order II. Phrynoidea (Pedipalpi, Thelyphonida). 



The thoracic segments are fused, and of the appendages only the last three 

 are walking feet, the third pair having the last joint (tarsus) developed into a 

 long many-jointed tactile flagellum. The chelicerae are strong and spined, but 

 end in a pincer in some species. The chelicerae are also clawed and are possibly 

 poison organs, since the bite of these animals is feared. The abdomen consist 



