226 SCORPIONS. SUBDIVISIONS OF TRACHEARIA. 



of these are severe, they are seldom, if ever, fatal, except in 

 persons previously unhealthy. It is not generally known, that a 

 small species of Scorpion exists in our own country, as well as on 

 the Continent of Europe; and this has afforded to European 

 Naturalists an opportunity of watching its hahits. The female 

 resembles that of the Spiders in her attention to her young ; these 

 she carries on her back for several days, at first not quitting her 

 abode ; and she afterwards takes care of them for the space of a 

 month, by which time they are enabled to shift for themselves. 



ORDER II. TRACHEARIA. 



762. THE Arachnida of this order present a 'much stronger 

 resemblance to the class of Insects, than do any of the preceding ; 

 for they are characterised not merely by the nature of their respi- 

 ratory organs which consist of ramified tracheae, instead of pulmo- 

 nary sacs but also by the imperfect development of the circulating 

 apparatus, as well as by a certain degree of metamorphosis, 

 which has been observed in several of them. They may be 

 divided into three families, according to the form of the thorax 

 and abdomen, these characters being preferred, on account of 

 their being more easily recognised, in the minute animals of 

 which the group consists, than those founded on the structure of 

 the mouth and the mode in which the food is obtained. These 

 families are ; I. The PsEUDo-ScoRPioNiD^:, or False- Scorpions -, 

 are so named from the strong resemblance which some of them 

 bear to the preceding group ; these have the abdomen very dis- 

 tinct from the thorax, and marked with rings ; and are furnished 

 with large palpi, which are either formed like feet (Fig. 448), or 

 furnished with pincers (Fig. 449) : II. The PHALANGID.E, or 

 Harvest-men, which may be regarded as representing the Spiders 

 in the Tracheary Order; they have the thorax and abdomen united 

 into one mass, but the latter does not exhibit any division into 

 rings ; the palpi are thread-like ; and III. The ACARID^E, or 

 Mites, which have the abdomen united to the thorax, but alto- 

 gether unmarked by rings (Fig. 452). 



