310 Piroplasuiosis 
infect the fox and jackal with the parasite have been attended by 
failure. 
On the other hand, another parasite (P. gihsoni Patton), which is 
somewhat different to P. canis morphologically, is stated to produce 
infection both in dogs and jackals in India. 
Concerning the Ticks widch transmit Firojjlasnia. 
As I have already stated, piroplasmosis is conveyed to cattle by 
Boophilus and Ixodes ricinus, to sheep by Rhipicephalus bursa, to dogs 
by Rhipicephalus sanguineus and Haeniaphysalis leachi, and to horses 
by Dermacentor reticidatus. A number of other species of ticks ma}'-, no 
doubt, play a part as carriers, but the ones I have named are the chief 
vectors, and in each case they have been proved to transmit piroplas¬ 
mosis under experimental conditions. 
Since piroplasmosis only occurs in the presence of ticks, it is now 
generally recognized that to grapple with the problem of prevention 
a knowledge of their life habits is essential. In the time at my disposal 
I can only refer briefly to the subject. All Ixodid ticks lay eggs whence 
they emerge as hexapod larvae. As soon as their chitinous exoskeleton 
has hardened sufficiently, the larvae may feed upon a vertebrate host. 
After feeding, they remain quiescent for a period, after which they moult 
and emerge as nymphs. These feed again, undergo metamorphosis, and 
finally emerge as adult males or females. In the case of Boophilus we 
have a one-host tick, for it remains, as a rule, upon the host from the 
larval to the adult stage, moulting twice whilst remaining upon the host. 
In R. bursa we have a two-host tick, since it remains upon the host 
during its larval and nymphal stages, moulting once upon the host; 
it abandons the host as a fully-fed nymph, undergoes its metamorphosis 
upon the ground, and emerges as an adult, which has to seek a second 
host. All of the remaining pathogenic species of ticks above enumerated 
are three-host ticks, for they drop from the host when replete both 
in the larval and nymphal stages to undergo their metamorphosis upon 
the ground ; in other words, the larva, nymph and adult have each 
to seek a host. In all of the ticks here mentioned the sexes copulate 
upon the host, and the replete fertilized females drop to the ground 
where they seek shelter and oviposit. The number of eggs laid varies 
with the species and individual. Taking average figures from my raising 
notes: 
