[51] Adaptation of Ticks 329 



appears reasonable to suppose that when they infest human dwellings 

 it is because of birds being harboured there. The birds on which the 

 ticks have been found are nearly all domesticated. The natural hosts 

 of persicus and reflexus are commonly fowls and pigeons which doubtless 

 have served to spread the tick amongst other birds in their vicinity. 

 The thin skin of the bird seems peculiarly adapted for the successful 

 attack of the small larval tick, and the nesting or roosting habit of the 

 birds permits the ticks to drop off in situations adapted to the feeding 

 and other life habits of the nymphs and adults. Both species in their 

 mature stages are essentially night feeders, that is, they feed when the 

 birds are in the dark and asleep, and the ticks retreat into crevices and 

 dark places during the day-time. Where the ticks attack man they do 

 so at night-time. I assume that 0. talaje var. capensis, which has been 

 found in penguin's and other birds' nests, will be found to have a 

 similar life-history to the above ; the larvae should be found on the 

 birds in localities infested by the tick. 



Argas vespertilionis has never been found on other animals than 

 bats 1 . Here we have a host which retreats to dark places during the 

 day-time. The retreats of bats (hollow trees, beneath roofs of houses, 

 in caves and grottoes) are more or less permanent dwellings where the 

 ticks find shelter very much as do the Argasids above mentioned which 

 attack birds. It is clear that to secure the adult stages of this tick the 

 habitats of bats are the places in which to search for them. 



Group 2. 0. moubata and 0. savignyi. 



In this group the larvae are inactive, and the first stage nymph 

 attacks the host. This nymph feeds as rapidly (in the case of moubata) 

 as does the adult, i.e. in 10 minutes to one hour. Ornithodorus moubata 

 and savignyi seem to be peculiarly adapted to their hosts and the habits 

 of their hosts. All of the latter, i.e. man and the domesticated animals 

 possess thick skins. Man appears to be the chief host, at any rate of 

 moubata. The hairless human skin, coupled with man's ability to 

 remove his ectoparasites, renders prolonged parasitism difficult. Man 

 herds his animals into a limited space in immediate proximity to his 

 dwellings or resting places along routes of travel. Both species live in 

 hot dry climates where there is a largely unclothed human population. 

 The ground is for long periods of the year covered deeply with a layer 

 of dry dust or sand both in and out of dwellings. 



1 See footnote, p. 326. 

 N. i. • 22 



