KADES AND TICKS 643 



the Scotch Orders, and relaxes some of the regulations that 

 experience had shown to be unnecessarily irksome. 



The object of dipping is to ameliorate or prevent alto- 

 gether the attacks of parasites, viz. the kade, Melophagus 

 ovinus ; the louse, Trichodectes sphcerocephalus ; the sheep 

 maggot flies, 1 e.g. the green bottle, Lucilia sericata, and 

 the blue bottle, Calliphora erythrocephala ; the scab-mite or 

 itch-mite, Psoroptes communis ; and species of tick or Ixodes. 

 The Sheep-Dipping Orders referred to are directed against 

 the last-named pest, but they are defective in that they do 

 not prescribe double dippings with an interval of fifteen to 

 twenty-one days between the first and the second section of 

 the operation, in place of single dippings, which, as explained 

 on page 647, are incapable of effecting the object. 



Kades or Kaids are slightly flattened, six-legged, spider- 

 like insects, resembling flies without wings, which move 

 about in the fleeces of sheep, and live by now and then biting 

 and sucking blood. They may be got rid of by timely 

 dipping, and repeating the operation within three weeks, to 

 kill the forms which have within that period developed from 

 the egg, upon which dips exercise no injurious influence. 

 They are most abundant on sheep in poor condition, and 

 during winter when there is little sun, as they do not 'then 

 come to the top of the wool to bask and so get shaken 

 off. Their bite on man produces small, persistently itchy 

 swellings. 



Grass-ticks (eight-legged) fix themselves by sending 

 their rostrum into the skins of sheep and other animals as 

 horses, cattle, pigs, dogs, rabbits, and also men. The females 

 do not move about much after gaining a footing on an 

 animal's hide, but become fixed, and gorge themselves with 

 blood drawn from the unwilling host. They increase greatly 

 in size, and finally drop off into the grass to lay their eggs 

 From the eggs hatch young six-legged forms, which after 

 several moults attain the fourth pair of legs and the adult 

 condition. 



1 Dr R. Stewart MacDougall, who has been investigating the sheep 

 maggot flies on behalf of the Highland and Agricultural Society, with a 

 view to determining the species which strike the sheep, has proved that 

 the chief and commonest species is a green bottle, Lucilia sericata The 



-re also found 



