OF SOUTHERN AUSTRALIA. 197 



services to the farmer and grazier are invaluable. The greater 

 the number inhabiting a district the less our land- owners have 

 to contend against. I have observed their capacious stomachs 

 crammed with grasshoppers, and Dr. Cobb asserts that they 

 devour enormous quantities of Buhnus, the fresh-water 

 mollusc which serves as the host of the sheep-fluke. At a 

 certain stage the flukes leave the snail and go on to the grass. 



White Ibis in Swamp. 



When the grass is eaten by the sheep, numbers of the flukes 

 are absorbed, and thus enter the liver, producing a deadly 

 disease, from which large numbers of sheep annually die. 

 However, before the fluke leaves its host, along comes the 

 ever- watchful White -fronted Heron, a lover of juicy Buhnus, 

 and, destroying the host, involves vast numbers of the parasite 



