CHAPTER X 



SECTION I 



ARACHNIDAE INCERTAE SEDIS : THE ORDER 



PENTASTOMIDA : TONGUE WORMS: 



FAMILY LINGUATULIDAE 



Endo-parasitic Araclinida with an elongate, vermiform and annulated 

 body. Mouth parts rudimentary and surrounded by two pairs of hooks 

 which probably represent rudimentary mandibles and maxillae. Respira- 

 tion is cutaneous. Circulatory system wanting. 



The Linguatulidae comprise a small group of peculiar vertebrate 

 blood-sucking parasites which in the adult stage closely resemble worms, 



the body being cylindrical, elongated, and often annu- 

 Biological position of .... . . 



the Linguatulidae l ate d- * n spite of this superficial resemblance they 



are in no way related to the worms, but are in reality 

 degraded arachnids which, in correlation with their mode of life, have lost 

 nearly every trace of their arthropod ancestry. The larval stage, how- 

 ever, still has two pairs of short legs armed with hooks, and resembles 

 the degenerate Demodex and Pediculoides ; the muscles of the Lingua- 

 tulidae are striated, another character common to Arachnids. 



The Linguatulidae are chiefly found in the respiratory passages and the 

 alimentary tract of carnivorous animals and snakes ; rarely in birds and 



L .. fishes. A few have been recorded from man, and the 



Relation to disease ....... 



probability that they are more widely distributed than 



is known at present, adds to their importance as human parasites. 

 Linguatula serrata, Frolich, has been found both in its larval and adult 

 stage in the lung, liver and spleen of man, and Darling has recently- 

 recorded a larva of this species from the lung of a native of Central 

 America. In 1847 Porocephalus armiUatus was discovered by Primer 

 in the liver of Negroes in Cairo ; subsequently it was found by others 

 in the same situation. Porocephalus momliformis has been found twice 

 in man, once in the small intestine under the peritoneum in a native of 

 Sumatra, and again in the liver of a Filippino. Several other doubtful 



