Ticks and Disease. 
281 
H&mapliy sails. — Palpi short and somewhat triangular, the second joint 
much projecting laterally ; base of rostrum rectangular ; no eyes or anal 
plates. 
Dermaeentor . — Palpi short ; base of rostrum rectangular ; eyes present ; 
no anal plates ; scutum generally with coloured markings ; coxrn IV of the 
male much enlarged. 
Ixodes. — Palpi long ; base of rostrum somewhat triangular ; no eyes ; male 
with ventral plates ; stigmata oval ; no festoons. 
Hyalomma. — Palpi long ; eyes present ; anal plates in the male ; body long 
oval ; stigmata triangular or comma-shaped. 
Amblyomma . — Palpi long ; eyes present ; no anal plates ; scutum generally 
with coloured markings ; stigmata triangular. 
Aponomma . — Palpi long ; no eyes or anal plates ; body broad oval ; scutum 
often with metallic spots. 
As ticks of the genus Aponomma live almost exclusively 
upon reptiles, they are without economic importance. All 
the other genera furnish species which are either proved to be, 
or are suspected of being, the agents in transmitting diseases to 
domesticated animals. 
The following diseases have been definitely traced to ticks: — 
Texas fever or redwater in cattle, prevalent in Europe, Asia, Africa, North 
and South America, and Queensland. It is conveyed by ticks of the genus 
Boophilus. 
Rhodesian fever in cattle is communicated by Rhipiceplialus appendi- 
culatus. 
Careeag, a European sheep disease, is spread by Rhipiceplialus bursa. 
Heartwater , which affects sheep and goats in South Africa, has been traced 
to the “ bont tick,” Amblyomma hebrceum. 
Canine piroplasmosis in various parts of the world is certainly conveyed by 
two ticks, Rhipiceplialus sanguineus and Hce nap hy sails leachi ; and other ticks 
are suspect, especially the English tick, Ixodes ricinus. 
Spirochcete disease in fowls, and probably also in man, is conveyed by Argas 
perslcus. 
Spirochcete disease in man in South Africa has been traced to Ornithodorus 
moubata. 
In these cases the chain of evidence is complete. Dogs in 
England bitten by adult ticks of the species H. leachi , taken 
from diseased dogs in South Africa, develop piroplasmosis 
within three weeks, and die of that disease. In the case of 
Rhodesian fever the infected larva of R. appendiculatus, 
communicates the disease after becoming a nymph, and the 
infected nymph after becoming adult. The Texas fever ticks 
not only convey the disease in all stages, but their very eggs 
are infected, and the young which hatch out may infect the 
first cattle they attack. In other cases a remarkable corre- 
spondence has been observed between the distribution of the 
tick and that of the disease, but the last link in the chain of 
proof — the infection of sound animals by infected ticks from 
another part of the world — is still wanting. 
Cecil Warburton. 
Zoological Laboratory, 
Cambridge. 
