126 ACAEINA OR MITES. 



redwater or Texas fever and East Coast fever in cattle, of 

 malignant jaundice in dogs, of heartwater in sheep, and human 

 tick fever, (Sec. 



The Ixodidffi are divided into two suh-families : — 



(i) Ixodince, which have the rostrum terminal in all stages, 

 (ii) Ari/aiitinii', in vi'hich it is inferior in the adult and 

 sub-terminal in the larva and nymph. 



The Ij'odinw are the so-called Hard Ticks, the dorsum of the 

 body being protected by a shield or scutum, and the posterior 

 part of the body may be cut into festoons, especially in the 

 males. The scutum is small in the females, large in the males. 

 They are all fixed parasites, and Trhen the female has laid her 

 one batch of eggs she dies. It is these IxodinK^ which carry 

 the animal diseases such as redwater, carried by RliipocepTioluy 

 (BoopMlus) unnulatus, and which attacks only one host. In 

 this case the larvse, coming from ova laid by the tick that has 

 fed on a beast with redwater, is pathogenic, and so gives the 

 disease to its host carried on from the parent. But in the case 

 of the carrier of the piroplasmae of malignant jaundice — a tick 

 called Hcamaplitjticdlif. — the parasites are not ready for the dog 

 until the ticks have become mature — that is, larvfe and nymphse 

 coming from the ova of a female that has fed on a jaundiced 

 dog cannot give the disease, but the adult can. 



The Anjantimi' are the Soft Ticks, and these have no dorsal 

 shield, and the head is not visible from above, but lies in a 

 shallow groove {rainerdgtone). The adults do not attach them- 

 selves permanently to their host, but only go to feed, and then 

 crawl away. They attack birds and mammals and man. Instead 

 of dying when eggs are laid as the female Ixodine doe.s, they live 

 and grow for years, and the female produces many batches of eggs. 



One well-known species is the Fowl Tide {Argas pcr.<iciu^), 

 wliich spreads the fatal disease " spirillosis." Another, once 

 found in Canterbury Cathedral, A. refie.riift, especially attacks 

 pigeons, its bite often proving fatal. Here also comes Ornifho- 

 doruif inouhafii, the carrier of African tick or relapsing fever. 



