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SOME NOTES ON THE BIONOMICS OF ORNITHODORUS SAVIGNYI 



IN BRITISH SOMALILAND. 



By R. E. Drake-Brockman, M.R.C.S., L.R.C.P. 



In the Somali country this tick is found in the soil in or around the huts on the 

 outskirts of the coastal towns, showing a predilection for the more squalid and 

 insanitary areas where the indigent Somalis reside. In the interior it frequents 

 most camps of long-standing which are inhabited by human beings and their domestic 

 animals. They are extremely common in the dusty soil surrounding the wells and 

 waterholes. In the waterless Hand and the Nogal Valley they are most frequently 

 found under large trees, especially when these are in isolated positions, as at Ged 

 Aboukir on the Arori Plain, and afford the only shade for miles to the shepherd and 

 bis flock during the heat of the day. 



Ornithodorus savignyi is capable of living for months without a fill of blood in the 

 soil, into which it burrows to a depth of half to one inch, lying dormant there until 

 the ground is disturbed by the foot of man or beast. In captivity it will hve for six 

 months and more in a tightly-stoppered bottle half-filled with dry earth, without 

 food or water. It will attack human beings, camels, cattle, ponies, mules, donkeys, 

 sheep and goats with equal vigour. 



When the soil in which it lives has been disturbed, it will move rapidly over the 

 surface until it finds its victim, losing as Httle time as possible before it starts to feed. 

 It seldom climbs much higher than the ankles in human beings and the hocks in 

 animals. 



The actual time occupied by the tick in getting its fill of blood varies, according to 

 its size, from 20 to 45 or even 60 minutes. As soon as it is engorged with blood and 

 just previous to withdrawing its biting apparatus, it discharges a fluid per anum 

 which moistens the skin in the vicinity of the puncture. On withdrawal this fluid 

 enters the wound and is doubtless the cause of the subsequent irritation, which varies 

 in different individuals. In some cases the area of the irritation may be the size of 

 a half-crown piece or more. 



Various methods have been suggested for destroying these ticks, but httle of any 

 practical value can be done owing to their wide distribution. In confined areas 

 where they swarm, such as the immediate vicinity of wells, the best and cheapest 

 method to adopt is to cover the whole infested area with dry grass and brushwood, 

 after harrowing or disturbing the surface, and then setting fire to the grass all round 

 simultaneously so that the fire will gradually burn its way towards the centre. 



Spraying the ground with various antiseptics has been suggested, but this method 

 is not only costly but quite useless, as, experimenting with several strong solutions, 

 I have found total immersion of the ticks for an hour and more quite ineffective — 

 the poison having little or no effect on them. After an immersion lasting two hours 

 of a number of half- and full-grown ticks in solutions of 1 in 500 carbolic acid and 



