PULMONAEY ARACHNIDANS. 369 



jaws are also armed with sharp and hooked fangs, and perforated near 

 their points for the emission of a poisonous secretion provided for the 

 destruction of their prey, the venomous properties of which emulate 

 that of the most formidable Serpents, and in like manner speedily ter- 

 minate the sufferings of the victim. 



(954.) Beginning with the first division, we shall now proceed to 

 place before the reader such facts as have been ascertained, connected 

 with the anatomical structure of the class under consideration. In 

 the Acaridce, or Mites, the skin of the entire body is so soft, that any 

 annulose structure is scarcely distinguishable ; the division, however, 

 into ceplialotJiorax and abdomen is sufficiently evident. The eyes are 

 minute black points, never exceeding four in number, and resembling 

 the ocelli of insects. Eight feeble legs are articulated with the thorax, 

 properly so called. The mouth seems adapted to suction ; and the jaws 

 form a piercing instrument barbed at the extremity. The structure 

 of the respiratory stigmata or spiracles would seem to differ very 

 considerably from those of insects. According to Audouin, in the 

 species which he examined (Ixodes Erinacei*), each spiracle resembles 

 a spherical tubercle perforated by an infinite number of small holes, in 

 the centre of which may be remarked a larger circular plate ; and it is 

 through these numerous foramina that the air enters the body and gets 

 into the trachea. 



(955.) The Pulmonary Arachnidans, both of the pedipalp and spinning 

 divisions, are strictly carnivorous in their habits, living upon the juices 

 of the insects they destroy ; and we may consequently expect, in the 

 construction of their alimentary apparatus, a simplicity proportioned to 

 the facility with which highly nutritive food composed of already-ani- 

 malized materials is capable of being assimilated. The mouth varies 

 somewhat in its conformation ; and if we compare the pieces composing 

 it with those we have found mandibulate insects to possess, we shall 

 have good reason for surprise in noticing the strange uses to which 

 some parts of the oral apparatus are converted. In Scorpions (fig. 184), 

 the apparent representatives of the mandibles of an insect are trans- 

 formed into a pair of small forceps, each being provided with a moveable 

 claw ; these, therefore, of themselves form prehensile organs adapted to 

 seize prey and hold it in contact with the mouth. But it is in the 

 maxillce that we find the most extraordinary metamorphosis ; for the 

 maxillary palpi, so small in insects, are found to be developed to such 

 prodigious dimensions, that they far surpass in size and strength any of 

 the ambulatory extremities, and, from their resemblance to the claws of 

 Crustaceans, have given the character from which the name of the 

 division is derived f. Each of these formidable organs is terminated by 

 a strong pair of pincers, and thus the maxillary palpi become con- 



* Cyclop, of Anat. and Phys., art. " ARACHNIDA." 

 t Pes, a foot ; palpus, a feeler. 



2s 



