35 THE ANIMAL PARASITES OF MAN 



tracheata, Arachnoidea, Myriapoda, 1 and Insecta or Hexapoda}, of which 

 only the Arachnoidea and the Hexapoda interest us here. 



A. Arachnoidea (Spiders, Mites, &c.). 



The head and thorax are always united together ; the abdomen 

 is either segmented or without exterior segmentation, in which case 

 it is united with the cephalothorax. 2 The number of pairs of appen- 

 dages amount to six, of which the two front pairs, the chelicerae 

 and the pedipalpi, are attached to the head region and the four 

 remaining pairs to the thoracic region. 3 The abdomen in the 

 adult condition has no appendages. The arachnoids are air- 

 breathers, and for this purpose are either provided with trachea?, 

 or with so-called lung sacs, or they breathe through the surface 

 of the body. 



There are eight or ten orders of arachnoids, of which, however, 

 only two, the Acarina and the Linguatulida, have to be considered 

 here. 4 



Order Acarina (Mites). 



Small arachnoids, the three parts of the body of which are, as a rule, 

 coalesced ; it is only rarely that a faint line indicates the division. The 

 two appendages on the head are designed for biting or puncturing and 

 sucking, and vary according to their use. The chelicerae 5 are fang-like 

 jaws or puncturing bristles, the pedipalpi are claw-like or sheer-shaped, or 

 form a suctorial proboscis/' The four pairs of legs are usually well 

 developed, more rarely they are rudimentary or have partly vanished ; 



1 R. Blanchard has compiled thirty-five cases in which Myriapoda have been 

 observed in the intestine as well as in the nose of human beings (" Sur le pseudo-par 

 d. myriap. chez I'homme," Arch. d. parasit., 1898, i., p. 452). E. Munoz Ramos reports 

 an additional case (ibid., p. 491) : A few years ago a doctor in East Prussia sent me 

 a rain-worm out of a lady's nose (compare Hanan, A., " Wahrsch. Pseudoparas. v. 

 Schweiss fiiegenlaro. u. angebl. Paras, v. Regenwurmern b. ein Hysterisch.," Arch. d. 

 paras., 1899, ii., p. 23). 



a [This is only so in the Acarina or Mites, not in the Araneida or spiders. F. V. T.] 



3 [The true character of the Arachnoidea is the presence of four pairs of ambulatory 

 appendages. This number is reduced to two pairs in the gall-making Phytoptidae. 

 F. V. T.] 



4 Chelifer cancroides has also been observed as a pseudoparasite in man (Arnault 

 de Verey, S. " Pseudopar. du chel. cancr. chez I'homme" (C. R. soc. biol., 1901, liii., 

 P. 105). 



5 [The Chelicerae are sometimes regarded as modified antennas, but it is more natural 

 to regard them as the morphological equivalent of the mandibles of Hexapoda. F. V. T.] 



6 [The pedipalpi or second pair of jaws consist of a stout basal joint and a palp, 

 which may have the appearance of a leg in Arachnida ; this may end with or without 

 a claw or with a chela (scorpions) ; they may also form a tube enclosing the styliform 

 chelicerse (mites). F. V. T.] 



