40 Giiidc to Insects and Ticks 



condition, \Yhich is reached in about twelve days from the time of 

 the hatching of the egg. 



Lice are commonest in the poorer districts of a town, and 

 spread rapidly among the children in a school. In times of war 

 lice are apt to become particularly troublesome owing to their 

 rapid increase in numbers, and the ease with which they can 

 spread in the crow^ded hfe of a camp ; the men have usually but 

 few opportunities for effecting a complete change of garments and 

 otherwise cleansing themselves, and so the conditions are favour- 

 able for a continuance of the infestation. 



The attention of visitors is directed to a pamphlet entitled 

 " The Louse and its Eelation to Disease," which can l^e purchased 

 in the Museum for a pe-nny. 



TICKS AND DISEASE. 



The transmission of several diseases caused by blood-parasites, 

 known as spirochaetes, may be traced to the Ijite of ticks, c.<j., 

 human tick-fever or relapsing fever of tropical Africa, due to 

 S2nrochaeta diittoni Novy and Knapp (fig. 13), conveyed from one 

 person to another by the tick OrnitliocJoros mouhata Murraj- 

 (fig. 14) ; and spirochaetosis in fowls and cattle, the fowl-tick 

 being Argas imrsicus Oken. A typhus-like disease in man, known 

 as Eocky Mountain spotted fever, is spread by the tick Dermacentor 

 venustus Banks, and a recently observed obscure affection known 

 as tick-paralysis in man, sheep and dogs, has also been shown to 

 be due to the effects of tick-bites. Concerning the blood-parasite 

 of heartwater of sheep, etc., conveyed by the bont tick, Amhhiomma 

 hebraeum Koch, in South and Central Africa, but little is known. 

 A somewhat similar disease, the East Coast fever of cattle, is due 

 to Thcilcria, a blood-parasite which occurs within the red blood- 

 corpuscles of the host, like the forms of PiropJasma {Babesia and 

 Nattallia), which cause redwater or Texas fever of cattle in many 

 of the warmer parts of the world, malignant jaundice of dogs in 

 India and South Africa, biliary fever of horses in Africa and India, 

 and carceag of sheep in Southern Europe, all transmitted by ticks 

 of the genera Rhipiccphalns, Margaropus, and their allies. 



In one of the two sloping-faced cases in the middle of the Hall, 



