604 GLOSSARY. PARASITE. 



while on the human body, but after three or four weeks spon- 

 taneously becomes extinct. 



No management of the health in animals will save them from 

 scab and mange if contact with affected animals be permitted ; 

 nothing but the effectual separation of the diseased from the 

 healthy can be of any avail. 



Maggots for example, those of the large blow-fly (Musca vomi- 

 toria or Sarcophaga carnaria), from which sheep often suffer so 

 dreadfully are not properly parasites ; even men are not exempt 

 from the attacks of such maggots. 



Lice, however, are unquestionably within the description of para- 

 sites. Some naturalists have bestowed much attention on this 

 subject, and they have been carefully reduced to orders, sub-orders, 

 families, genera, and species. It will be enough, however, to re- 

 fer to some of the best-known genera and species. Hcematopinus 

 is a large genus, in which the louse of the ox, the calf, the pig, 

 and the dog are found. A species of the same genus frequents 

 the skin of the ass, and the same is sometimes found on the horse. 

 The Hcematopinus vituli is said never to be found on the ox. The 

 Hcematopinus canis is not of common occurrence, but is said to be 

 found also on the ferret. 



Trichodectes is another genus ' in which parasites commonly 

 known as lice affect some of the animals of the farm. 



Trichodectes equi, louse of the horse, is common both on the 

 horse and ass, especially when fresh from pasture. 



Trichodectes scalaris, louse of the ox, is common on cattle, 

 especially on the mane. It is sometimes found also on the ass. 



Trichodectes sphcerocephalus, the louse of the sheep, has an 

 orbicular head. 



Trichodectes latus, the louse of the dog, is more especially com- 

 mon on puppies. 



The common flea (Pulex irritans) is but approximatively a para- 

 site. It frequents the skins of animals in general, but does not 

 breed there. One of the best remedies is the Persian insect-pow- 

 der, obtained from the Pyrethrum roseum, and sold in india-rubber 

 balls. 



The gad-fly ((Estrus bovinus) has called forth long dissertations. 

 It attacks the ox, the cow, the horse, and even human beings. 



Ticks are found on the skins of horses, cattle, sheep, and 

 dogs. 



The Hippoloscce must be distinguished from ticks. The Hippo- 

 boscce live exclusively on quadrupeds and birds. The ass suffers 

 much more from them than the horse. They abound most on 

 white and light-coloured horses. Several allied genera occur in 

 this country, and are found on various birds. The Craterina hir- 

 undinis deposits its eggs like a cocoon in the nest of the swallow. 



