SEVENTEENTH ANNUAL REPORT. 



431 



Rhipicephalus australis, n. sp. 



Female.— When replete, measuring 10-11 mm. in length and 6-7 mm. in breadth. 

 Dorsal shield smaller than that of annulatus and greater than that of decoloraius, 

 of the same form and with similar furrows. Eyes, pale. Labium with eight rows 

 of teeth. Mandibles with the lesser process tricuspid, and presenting a rounded 

 process as well. 



3fale, adult. — Approaching that of annulatus, but with adanal shields more chiti- 

 nous, and also exhibiting a caudal appendage. Neither the shields nor the "tail" 

 are so pronounced as those of' decoloratus. 



Habitat. — On horses, cattle, etc. ; northwest to northeast Australia. 



For some time now there appears to have been doubt as to the identity of the Red- 

 water ticks of Australia and North America with one another, and also with the 

 supposed carrier of Red water in Cape Colony — the Common Blue, or Blood, Tick. 

 With the object of settling this point, at any rate so far as the common species in 

 Cape Colony is concerned, a careful study has been made of these three forms, and 

 the following notes are the results of these comparisons: 



The fact that Redwater is carried from beast to beast by the agency of ticks 

 was discovered but a few years ago by official investigators in the United States of 

 America, where the disease has been the direct cause of great losses from time to 

 time. These investigators found that one kind of tick, Rhipicephalus annulatus (Say) 

 or, as it is more commonly known, Ixodes bovis, was the agent which disseminated 

 the disease, and proved that not only did the bites of the ticks produce the disease, 

 but, further, that the disease, or power of producing it, was communicated from the 

 maternal tick through its eggs to the young. Subsequently, when this Redwater broke 

 out in Queensland, Australia, it was found associated with a tick which many of us 

 regarded as identical with the American one, and as this tick spread from district tc 

 district, so the disease spread with it. In Cape Colony, Redwater has been gradually 

 extending its range from the north along the eastern seaboard, and the common 

 Blue, or Blood, Tick is no doubt the chief distributing agent. This species is referred 

 to as the supposed or chief distributing agent of the disease, because of the great 

 possibility that it is not the only agent, nor the only tick, for there is a probability 

 that some, if not all, of our other common species, such as the larger Blue, the Red,^ 

 and the two Bontes,^ may also act as transmitters; a probability enhanced by the fact 

 that these investigations have shown that the Australian, the North American, and the 

 local Common Blue, though closely allied and of the same genus, are distinct species. 

 But as, up to the present, there does not appear to be any conclusive technical evi- 

 dence upon this important point, I venture to draw attention to it as being a question 

 invested with so much interest and practical importance that it is well worthy of 

 attention, particularly in Cape Colony, where the opportunities of investigating it 

 are so great. 



Another interesting feature is that whilst in Australia and, I believe, the United 

 States too, the ticks were strangers to those parts to which they carried the disease, 

 such is not the case in Cape Colony. Our Blue Tick {Rhipicephalus decoloratus Koch) 

 occurs in many parts of the colony, and is found where, I am given to understand, 

 Redwater has never been known and where cattle could not have become immune. 

 That the ticks are actually dissociated from the disease in these parts is proved by 

 the fact that imported cattle do not contract Redwater when brought into contact 

 with the native cattle. In Australia and North America the ticks have never, to my 

 knowledge, been reported as so dissociated from the disease, and fever-stricken cattle 

 were always infested with a particular tick, and unless a beast was actually immune 

 by birth or had become so by previous infection or inoculation, the bites of these 



*Red tick=Rhipicephalus Evertsi. The Bonte tick=Amblyomma hebrseum. The 

 Bonte leg tick=IIyalomma segyptium. 



