ANNULOSA: ARACHNIDA. 325 



nature. They live under stones or in dark crevices, and run 

 swiftly, carrying the tail curved over the back. They feed on 

 insects, which they hold in the chelate palpi, and sting to 

 death. The largest forms, from Central Africa and South 

 America, attain a length of nine or ten inches. 



Family 2. Thelyphonidce. The members of this family in 

 external appearance closely resemble the true Spiders, from 

 which they are separated by the possession of a segmented 

 abdomen, and long spinose palpi, and by the absence of spin- 

 nerets. They are distinguished from the Scorpionidcz by the 

 amalgamation of the head and thorax into a single mass, which 

 is clearly separated from the abdomen by a constriction, as 

 well as by the fact that the maxillary palpi terminate in mov- 

 able claws instead of chelae. Further, the extremity of the 

 abdomen is not furnished with a terminal hook or " sting." 



In Thelyphonus (fig. 166, C) the abdomen terminates in 

 three post-abdominal segments, to which a long many-jointed 

 caudal appendage is attached ; but in Phrynus the abdomen 

 ends in a button-like segment. The first pair of legs is the 

 longest (immensely so in Phrynus), the fakes are not chelate ; 

 and the maxillary palpi, though of large size, and sometimes 

 didactyle, do not form true chelae. The genus Thelyphonus is 

 confined to the tropical parts of Asia, America, and Australia, 

 and the genus Phrynus is also wholly tropical. 



ORDER II. ARANEIDA or SPH^EROGASTRA. This order in- 

 cludes the true Spiders, which are characterised by the amal- 

 gamation of the cephalic and thoracic segments into a single mass, 

 and by the generally soft, unsegmented abdomen, attached to the 

 cephalothorax by a constricted portion, or peduncle. Respiration 

 is effected by pulmonary sacs in combination with trachece. (Hence 

 the name Pulmotrachearia, sometimes applied to the order.) 

 The number of the pulmonary sacs is smaller in the true Spiders 

 than in the Scorpions, being either two or four, opening by as 

 many stigmata upon the under surface of the abdomen. Usu- 

 ally there are only two pulmonary stigmata, placed just be- 

 hind the peduncle which unites the cephalothorax with the 

 abdomen, on the lower surface of the latter. In the Mygalidcz 

 there are two posterior stigmata, leading into pulmonary sacs ; 

 and in other genera there are also two additional stigmata, 

 which, however, open into tracheae, and not into pulmonary 

 sacs. 



The head bears two, four, six, or eight simple eyes ; the 

 mandibles are simply hooked, and are perforated by the duct 

 of a gland which secretes a poisonous fluid ; and the maxillary 

 palpi are never chelate. The maxillary palpi of the females 



