TICKS OF THE BELGIAN CONGO. 343 



meal of blood, the total number of eggs laid by each female being 100-150. The eggs, 

 like those of other ticks, are agglutinated in masses and are much larger than in 

 IxoDiDAE. By the 6th day, at 29° C, the larva has developed within the egg, but 

 is a helpless creature incapable of feeding. Whilst still in the egg-shell the nymph 

 develops within the larval skin, and usually about 10-15 days after the eggs were laid 

 the nymphs emerge, throwing off the egg-shell plus the larval skin. . The nymph is 

 known as a first stage nymph, for there may be three or four nymphal stages passed 

 before the tick attains sexual maturity. The first stage nymph is ready to feed very soon 

 after emergence, and, having gorged, it undergoes metamorphosis and moults to feed 

 again as a second stage nymph, etc. The nymphs and adults take 10-120 minutes 

 to feed. The adults pair away from the host. This tick lives for many months when 

 unfed ; in the laboratory it has survived for two years. Depending on temperature, 

 it may take a year or two to complete its life-cycle. 



Relation to Disease : 0. ynouhata conveys relapsing fever to man in many parts of 

 tropical Africa, where the tick is widely distributed. When the tick imbibes blood 

 containing Spirochaeta duttoni, it is capable of infecting persons upon whom it sub- 

 sequently feeds. The progeny of an infected female remains infective up to the third 

 generation and perhaps longer. The spirochaetes are therefore parasites both of man 

 and of the tick. When feeding, the tick frequently exudes white excreta and a watery 

 fluid, the latter issuing from large pores between the first and second legs on each side. 

 This fluid prevents the coagulation of the blood. The excreta are infective, and the 

 spirochaetes may enter the wound either from the excreta mixed with the anti- 

 coagulating fluid about the bite, or more directly through the mouth-parts of the 

 tick. 



Prevention : When possible, infested quarters should be destroyed by fire. Native 

 huts where ticks occur should be shunned. Sleeping in hammocks and under mosquito 

 nets affords protection. The ticks may be encountered in resting places and old camps, 

 and may be transported in a traveller's luggage. 



Haemaphysalis leachi requires three hosts upon which to feed in the larval, nymphal 

 and adult stages. The female may lay up to about 5,000 eggs, whence the larvae 

 emerge in about 30 days at 20° C. After a week or so the larvae are ready to 

 feed. They remain 2-7 days upon the host, as do also the nymphs which emerge from 

 the larval skins after 30 days or so. The gorged nymphs, having in turn dropped 

 from the host when fully fed, undergo metamorphosis upon the ground in 15 days at 

 24° C, when the adults, male and female, emerge. Both sexes attach themselves 

 readily to the host, at first they scatter, but after 2-3 days pairs may be found attached 

 close together. They copulate upon the host, the female usually taking 12 days to 

 feed, whereas the male may remain attached for weeks. The female begins to oviposit 

 after 3-5 days at 23° C. Under optimum conditions the life-cycle may be completed 

 in 123 days. 



Relation to Disease : H. leachi is the usual carrier of canine piroplasmosis in Africa, 

 being distributed throughout the continent. It occurs most commonly on Carnivora, 

 being specially noticed upon the dog. When a female tick feeds upon an infected dog 

 the parasites undergo development in the tick and penetrate the ova. The ticks' 

 offspring are not capable of conveying the disease until they attain sexual maturity. 



