390
The Ticks of East Africa
without leaving the host. The resultant adults feed on the same animal and,
in due course, the female drops to the ground to oviposit.
R. bursa and R. evertsi are two-host ticks. In these cases again, the larva
feeds and develops into a nympha on the host. The fully-fed nympha, how-
ever, drops off and, after ecdysis, the adult that emerges has to find a second
host. As in the previous instances, the female engorges and falls to the ground
to lay eggs.
All the known East African species of Hyalomma are either three-host
ticks or they may be partially three-host ticks. A brood of larvae fed on a
rodent will feed and drop off first as a batch of engorged larvae ; another lot
of the same brood, put on the rodent at the same time, will feed and moult to
nymphae without dropping off ; the engorged nymphae, however, will always
leave the host to moult on the ground. The nymphae from the engorged
larvae which dropped have to reach another host ; they will again fall off as
engorged nymphae and undergo ecdysis. The adults, of course, require, in
this case, a third host. When larvae of Hyalomma are fed on cattle, sheep,
or poultry, they drop as engorged larvae and the life-history is continued as a
three-host type.
The larva of A. persicus is the only instar of that species which attaches
itself to its avian host for several days. It feeds for five or more days, falls off
and develops into a first nympha. The tick from now on, feeds only for about
one or two hours at a time ; and preferably at night or in the dark. The first
nympha feeds for this short period, leaves its host and, in a fortnight or so,
casts its skin to emerge as a second nympha. It again takes a meal and creeps
away to develop into an adult. The female feeds at intervals between which
she deposits her batch of eggs in sheltered places. The Argas species differ
from those already mentioned in that they have two or more nymphal instars,
in their manner of feeding and in the intermittent way the female lays her eggs.
The development of Ornithodoros species is still different. O. megnini
may be classified as a one-host tick. The larva feeds deep inside the ears ;
it moults to a nympha on the host. The replete nympha falls off and develops
into an adult which, if a female, lays her eggs after fertilization. Neither the
male nor the female is normally found on animals, for the nympha has ac-
quired sufficient food to sustain the adults in their main function in life.
Incidentally, the nympha usually remains on the host for about a week to a
few days over a month ; but it may remain attached for several months—
even up to seven months.
O. moubata presents yet another kind of life-history. The female lays her
eggs in batches. The larvae that hatch out are unable to feed. After a short
period of quiescence, they develop into nymphae. These feed at intervals ;
and between each meal. Lasting from 15 minutes to over two hours, they
undergo ecdysis. The male nymphae moult from three to five times, the
female nymphae from three to seven times, before developing into adults.
O. moubata, therefore, is an intermittent feeder and attacks a host for short
periods only.
There are other aspects of tick-life that need closer attention. For in-
stance, larvae of Hyalomma will feed very indifferently on hares, cattle, and
sheep for the most part of a year. Yet, at other times, they will feed readily