388 MANAGEMENT AND FEEDING OF SHEEP 



food consists wholly of blood, which they take through 

 the proboscis with which they penetrate the skin. 



The injury which they inflict comes chiefly from the 

 prolonged itching which follows the puncture of the skin. 

 ^Vhen present in large numbers, the annoyance resulting 

 is very great. When the wool is removed by shearing, 

 the ticks, in great measure at least, leave the old sheep. 

 They either perish or become transferred to the lambs. 

 To these they are oftentimes a source of great annoyance, 

 because of their numbers, and also because of the greater 

 ease with which they may puncture the tender skin of the 

 lambs. Evidences of the discomfort are manifested in the 

 extent to which they bite at themselves and rub against 

 external objects. For treatment see Chapter XX. 



Sheep scab is so called from the scabs which come on 

 the skin and which are the outcome of inflammation re- 

 sulting from the innumerable bites of the scab mites when 

 taking their food. Three classes or species of scab mites 

 infest sheep. The first is known as Sarcoptes scabiei, the 

 second as Chorioptcs communis and the third Psoroptcs 

 communis. The first causes scab on the head the second 

 scab on the feet, and the third scab on various parts of 

 the body. That named last is by far the most common 

 of the three and also by far the most harmful. The life 

 history of the three is very similar. 



The scab mite (Sarcoptes scabiei) is so small as to be al- 

 most invisible to the naked eye, but its presence may be 

 known by the scabs which result and the location of these. 

 They are first noticed on those portions of the head that are 

 comparatively free from hair and grease, as on the upper 

 lip, the nostrils and around the eyelids and ears. From 

 these starting points they gradually spread over various 

 parts of the head. For treatment the application of some 

 one of the approved scab dips or ointments (see Chapter 

 XX) will suffice in the early stages of the infection, but 

 in the more advanced stages it may be necessary to first 



