700 MEDICAL ENTOMOLOGY 



CLASSIFICATION 



The family Linguatulidae is divided into three genera, which may be 

 distinguished by the following key : 



1. Body flattened ventrally, rounded dorsally and tapering poster- 



iorly ; haematocoele forming pockets in the lateral rings . Linguatula. 

 Body not so flattened ........... 2 



2. Body cylindrical and ringed ; haematocoele continuous . . Porocephalus. 

 Body cylindrical but not ringed ...... Reighardia. 



Sambon has created a fourth genus, Raillietiella, for three species in 

 which the posterior extremity is bind, the female sexual opening is at 

 the anterior end of the abdomen, and in which there are three vesicular 

 protuberances around each hook pit. 



GENUS LINGUATULA, FROLICH 



Linguatula serrata, Frolich. The male is white and measures from 

 18 mm. to 20 mm. in length and 3 mm. in width ; the female is greyish 

 white and measures from 80 mm. to 100 mm. in length and from 8 mm. 

 to 10 mm. in width in front and 2 mm. behind. This species is 

 widely distributed in Europe, and appears to be common in certain 

 parts of France ; it is parasitic in the nasal and respiratory passages 

 of a number of animals, including the dog, fox, wolf, horse, goat and 

 sheep ; the larva is found in the horse, sheep and the ox ; the dog 

 appears to be the true host. 



The eggs are expelled from the nasal cavities of the dog by the 

 act of sneezing and fall on the ground, from which they may be 



blown about ; if they fall on grass on pastures, as may 



Life history and . , , , , , . ' 



bionomics occur in the case of sheep-dogs, they may be ingested 



by sheep and cattle, in the alimentary tract of which 

 they hatch out. The larva bores its way through the intestinal wall 

 and becomes lodged in some organ, usually the liver, where it passes 

 through a quiescent stage, changing once or twice until the nymph 

 is formed. This stage is very similar to the adult, but has numerous 

 spicules on the skin ; it wanders about in the body of the host until 

 it reaches the respiratory tract, up which it passes to find its way 

 out eventually through the trachea. It is not quite clear as to how it 

 gets back to the dog, but it is probably either through the alimentary 

 tract or up the nose ; it is always found in the nasal cavity, where 

 it becomes sexually mature. 



GENUS POROCEPHALUS, HUMBOLT 



This genus contains about twenty species, many of which are very 

 imperfectly known ; further study will probably reduce the number 



