644 MANAGEMENT OF SHEEP EXTERNAL PARASITES 



The sucking lice are represented on the sheep by 

 Trichodectes sphcerocephalus. It has a head as broad as 

 long. The general colour is whitish, with dark spots and 

 a dark head. These lice exist usually in greatest numbers 

 on the head and hairy parts of the body, and produce much 

 irritation, which prevents sheep from thriving. With a little 

 care, and by adopting the comparatively new practice of 

 dipping sheep over the head, they can be quite destroyed. 

 Most well-managed flocks are free from them. 



Black flies, which are found often in swarms in the 

 northerly parts of Europe and North America, are some- 



FlG. 53. Trichodectes sphcerocephalus (Nitzsch). 

 9 Dorsal surface, x 80. 



times a grievous pest to both animals and man. They 

 belong to the family Simulidce and the genus Simulium. 

 By means of their piercing mouth parts, the females make 

 wounds like mosquitoes and suck up blood. They may also 

 live by sucking any raw surface, as an accidental cut made 

 by shearing, or the crowns of rams that have been fighting. 

 When very numerous, these flies irritate and unsettle sheep, 

 and prevent wounds healing, especially if these be about the 

 top of the shoulder, where the animal can do little to protect 

 itself. The fles are small and black or greyish, with a humped 

 thorax, short antennae, and broad iridescent wings. Their 

 larvae are aquatic. 



The maggot flies, the green and blue bottle flies, do 



