It is significant that the Russian worker considers the 

 rabbit to be an atypical host of immature stages of H. excavatum . 

 This is far from true in North Africa and Arabia, where hares and 

 other smaller animals are frequently parasitized (rabbits do not 

 occur here). Most probably smaller animals are also parasitized 

 in Russia but workers there, who have been occupied chiefly with 

 veterinary problems, have failed to investigate this possibility. 

 Indeed, it seems that a diametrically opposed, theoretical con- 

 clusion might be drawn; 



Under primitive conditions, in areas lacking large 

 numbers of domestic animals, H. dxcavatum spends part 

 or all of its life cycle on small animals, usually no 

 larger than hares . In these situations it undergoes a 

 one or two-host type of life cycle. However, when herds 

 of larger domestic animals are present in the range of 

 this tick, the adiilts and sometimes the immature stages 

 may be confined to these animals. On these larger ani- 

 mals, H. excavatum undergoes a three-host type of life 

 cycle, "which is an atypical one for the species, in- 

 fluenced as it is by the availability of hosts due to 

 human activities. 



This matter is obviously in need of further investigation. 



With regard to the seasonal cycle of H. excavatum , the 

 aforementioned authors working in Iran, E^pt, and Palestine, 

 as well as Serdyiikova (19A6b) working in the semi-deserts of 

 Tadzhikstan, agree that engorged nymphs and young adults hi- 

 bernate in cracks and crevices of bxiildings during the winter; 

 the Soviet observer states that larvae may also overwinter under 

 these conditions. In Russia, hibernating ticks were taken in, 

 among, under, and in association with wooden fixtures of animal 

 enclosures, but not under cakes of dung plastered on loose walls. 

 When these structures were removed the incidence of ticks found 

 in these yards the following summer was only a fraction of what 

 it had been the previous year. In the deserts of Egypt engorged 

 nymphs and vinfed adults overwinter in rodent burrows. 



In spring, ticks that have hibernated venture forth to feed. 

 Under experimental conditions, if they are removed to a warmer 



- LUr- 



