UNKNO WN GERMS 



701 



americanus and the nymphs and adults oi D. variabilis ca.n transmit 

 the virus of Rocky Mountain fever. 



Enemies. — The enemies of ticks are numerous, and among them may be 

 mentioned fowls and blackbirds. 



Prophylaxis. — The prevention of ticks in cattle is a difficult proceeding. 

 The following are some of the methods in use (from Balfour and Archibald) : — 



Cattle Washes and Dips. — Arsenic used to be employed (Cooper's Dip 

 Powder), but was found to be dangerous. A useful oil is crude petroleum, 

 2 gallons; hard soap, ^ pound; and water, ^ gallon. The soap is dissolved 

 in the hot water and the petroleum gradually added. Five days' spraying is 

 advocated in place of the usual fortnightly dip. 



Rotation of Crops. — This is said to be useful in the United States. 



Burning of Pastures. — Not a good plan. 



Immunization. — Immunization by inoculation against babesia, etc. It is 

 not very useful. 



Quarantine. — Quarantine of cattle and control over their movements is 

 important. 



There are, however, a good many practical points to be attended to in 

 s_pra5ring or dipping cattle. Reference may be made to Cooper's paper in the 

 Journal of Agricultural Science, vol. iii., or to Newstead's Report of Twenty- 

 first Expedition of the Liverpool School of Tropical Medicine. 



Classification.— The Ixodoidea are divided into two famiUes: — 

 Family i: Argasid^ Canestrini, 1890. — Ixodoidea without a 



scutum; mouth parts of adult not prominent from above; no pul- 



villus attached to tarsus in adults. 

 Family 2: Ixodid^ Murray, 1877. — Ixodoidea with a scutum ; 



mouth parts prominent from above; pulvillus present, attached 



to the tarsus in adults. 



Remarks.— Neumann's classification is very diSerent from the one used in this 

 book. He recognizes ixodidae (=ixodoidea) divided into Ixodinae ( = Argasidse 

 and Ixodidae) and Spelaeorhynchinae, these last being parasites on bats. Other 

 classifications are those by Lahille and by Banks. 



Family t : Argasid^. 



These arachnids are more like bugs than ticks in their habits. 

 ^ During the day they are concealed in cracks in walls or floors, or in 

 gravel, but at night they come out and run about. Christophers 

 says that if handled they sham death, and that when running about 

 they have a curious habit of raising the first pair of legs as though 

 to receive information about their surroundings. They can live 

 for a long time (three to four years) without food. They generally 

 feed after dark, being gorged in about fifteen minutes. 



Donovan states that while feeding fluid is secreted by the coxal 

 glands, and lies between the parasite and the skin of the host. 

 This fluid is alkaline, and prevents coagulation of blood. After 

 feeding, the tick drops to the ground, and, being wet with secretion, 

 becomes covered with dust and dirt . At first they are much swollen, 

 but in a few days this diminishes, though they may remain dis- 

 tended for weeks. Soon after feeding, the tick moults, and then 

 becomes active again, and is ready for another feed. 



The Argasidae pair at various times, one female being fertilized 



