910 



DISEASES OF SHEEP. 



Fig. 1200.— Gad-fly, Greatly Magnified. 



'SHEEP-BOTS, OR GRUBS IN THE HEAD. — This disease is one 

 of the most serious with which the farmer has to deal, and one which 



should! be attended to 

 promptly ; and it is of 

 the utmost importance 



\ikteS^^K8^jKS^fe^^S ►y^** t^- t ' lat *' ie most thorough 

 ™B» •"■¥ & - • \tX^Bt mm mitm I -SL- means; should be re- 

 sorted to for preventing 

 it. It is caused by the 

 gad-fly, or breeze-fly 

 {(gstrus ovis, or ceph- 

 alemia ovis), which at- 

 tacks the sheep in the 

 nostrils and frontal si- 

 nuses, creating great 

 dread of it on the part 

 of the flock. When 

 struck by the fly, they 

 stamp the ground violently, and manifest every sign of great agony. 

 Deposited at the entrance of the nostril, the larva proceeds upward 

 to the farthest recesses. Fig. 1200 shows a greatly magnified rep- 

 resentation of the sheep gad-fly, and Fig. 1201 (#) shows the insect* 

 natural size, with its larva {a). .' ' i - 



The sheep gad-fly has a less hairy head, but one larger in pro- 

 portion to its size,, than the horse gad-fly. Its face is reddish, its 

 forehead brown, its antennae black or - 



brown, with, small black tubercles, and 

 belly spotted with white. . It lays its 

 eggs on the edges of the sheep's nostrils, 

 and the larva lives in the frontal and 

 maxillary sinuses. Its head is armed 

 with two horny black hooks, by which 

 it fixes itself to the mucous membrane, 

 and lives there in this state nearly a 

 year, when it falls to the ground, and 



burying itself a "few inches, soon merges into the chrysalis state. 

 Thirty or forty days after its burial, it develops into its perfect state, 

 and wings its flight. In this state it is scientifically known as the 

 conops, and lives' on humble-bees. It is to avoid the attacks of the 

 gad-fly in hot days that the sheep wil^ lie down with their nostrils 

 buried in dusty ruts, or stand up with their heads lowered between 

 their fore legs, and with their noses nearly in contact with the ground. 



Fig. 1201.— Gad-fly and Larva. 



