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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



specialization varies to some extent with the species. We see, for 

 instance, an example of the most complete form of parasitism in the 

 OX warbles of the genus Hypoderma; here the parasite has become 

 highly dependent on the host, and confines attack largely to one host, 

 the ox. The habit of the larvae of migrating to the back of the host, 

 where development is completed, and the fact that the larvae seldom 

 live if removed from the host a short time even before their normal 

 emergence, probably indicates a closer relationship to the host than 

 in the case of the horse bots or other members of the family. Although 

 this is an exceedingly interesting group of flies it is not my purpose to 

 dwell at length upon it, except to call attention to the occurrence of 

 some of the varied forms of myiasis produced. 



The sheep bot {CEstris ovis) is primarily a pest of sheep yet we find 

 that it attacks other animals and even man. Ed. and Et. Sargent^ 

 state that this fly attacks man in certain elevated regions in the Sahara 

 where sheep are less numerous than people. The eggs or larvae are de- 

 posited upon the conjunctival and nasal mucous membranes of man 

 and cause much trouble from March to June. In this country no 

 records have been made of myiasis in man produced by this species. 

 It is fairly common in nmny parts of the United States, and the habit 

 of the larvae of passing up the nostrils and into the sinuses of sheep is 

 well known. It is not usual for it to invade the tissues of the host 

 but appears to subsist on the mucous secretions. 



The ox warble {Hypoderma lineata) is our most important species, 

 in the United States. Its near relative, H. hovis, has recentty been 

 found by Drs. Hadwen and Hewitt to have a wide range in Canada, 

 and it is now probably within our northern border. Certain points 

 in the biology of our species have not been definitely deterrriined, and 

 these are giving rise to considerable discussion. The entomologists 

 in this country are inclined to the view that the larvae gain access to 

 the back of the bovine host by way of the oesophagus, while some 

 European authorities believe the larvae penetrate the skin along the 

 back or migrate beneath the skin from the legs to the back. It is not 

 my purpose to discuss the merits of the case. If it is true that the 

 larvae migrate from the oesophagus to the back, we have a case of a 

 combined internal, transient myiasis followed by dermal myiasis. 

 Cases of man being infested by larvae of this genus are not rare. In 

 some instances the larvae move about beneath the skin until mature, 

 while in other cases they have been recorded as developing at the root 

 of the tongue or within the orb of the eye. 



1 1913. Sargent, Ed. and Et. La "Tamne," myiase humaine des montagnes 

 saharennes tonareg, identique a la "Thimni" des Kabyles, due a (Estris ovis. Bull. 

 Soc. Path. Exot., Paris, VI, pp. 487-488. 



