ACABINA OR MITES. 127 



These ticks hide away in crevices, in buildings, in sand, itc, 

 and come out to feed when necessary. 



Ticks may be destroyed on slieep by dipping, and also, as is 

 now done in Africa, by spraying the cattle driven through 

 narrow runs. Burning of the grass on tick-infested land also 

 does some good. 



The following are pathogenic species : — 



Ch-nithodorus mouhata — On man, birds, &c. (human tick 

 fever, &o.). 



ArnMyomma hebrceum — On sheep and goats (heartwater). 



HcemaphsijlUs leachii — On dogs (malignant jaundice). 



Bhipoaephalus decoloratus — Cattle, &c. (redwater in 

 Africa). 



Rhipoeephalus australis — Cattle (redwater in Australia). 



RhipocepTialus annulatus — Cattle (redwater in America). 



Rhipoeephalus simus and Rhipoeephalus appendiculafua — 

 On cattle, &c. (East Coast fever in Africa). 



Ixodes ricinus — On cattle, &c. (redwater in Europe). 

 Family Sarcoptidse. — These minute mites live as parasites in 

 and upon animals and man. The body is round or oval ; in 

 front is a conical rostrum. The sexes are told by the differ- 

 ences in the legs and general shape of the body and by the size, 

 the male being always much smaller than the female. They 

 occasion diseases that are spoken of as Scabies or Psoric diseases. 

 The Sarcoptidse are the smallest of all mites, varying from •! mm. 

 to 1 mm. (2-3- inch) in length. No eyes are present, and respira- 

 tion is cutaneous. The Psoric Sarcoptidse attack the epidermis 

 of animals, and the punctures they produce, with the addition 

 of a poisonous saliva, give rise to thick crusts over their point of 

 attack. The Sarcoptidse are oviparous and ovoviviparous. The 

 eggs are slightly ovoid, and the contained embryo is easily seen 

 in an ovum in an advanced stage. The eggs incubate in a few 

 days. In some cases the author has observed the ova to hatch 

 in two days in the species producing Sheep Scab ; more usually 

 seven to ten days is the period. 



