180 
Notes 071 Tides 
indicating the parts of the cycle representing each successive stage in 
the tick’s development, commencing with the ovipositing female, after 
which follow the egg, larval, one or more nymphal and, finally, the adult 
stages (more especially the females). The blackened parts of the dial 
indicate the part of the life-cycle which is spent in sucking the blood 
of the host. The numbers alongside the five dials correspond to the 
following types of parasitism :— 
Type 1, represented by Argas pey'sicus, also probably by A. rejlexus 
and A. vespertilionis and some other species of Argas and Ornithodorus. 
It will be seen that only the larval stage remains attached to the host 
for some time (.5 to 7 days, or more) whilst sucking blood. The later 
stages are rapid and repeated feeders. There are at least two nymphal 
stages; the adults attack a succession of hosts and feed repeatedly, 
laying eggs in batches after each feed. There are many breaks in the 
chain of jDarasitism. 
Type 2, represented by Ornithodorus mouhata and 0. savignyi. 
The larva does not feed. The‘first stage nymph and the succeeding 
nymphal stages and adults are all rapid feeders and attack a number of 
hosts in succession. But for the inactive larval stage these ticks behave 
similarly to the ticks under Type 1, there being many breaks in the 
chain of parasitism. 
N.B. An aberrant type of parasitism is that of 0. megnini, in that 
the larval and nymphal stages (probably two or more of the latter) feed, 
whereas the adults do not. This type is not illustrated in the diagram, 
it has been fully described elsewherek 
Type S. This appears to represent the commonest form of para¬ 
sitism in Ixodidae. It has been observed, for instance, in the following 
species, which have been raised experimentally: Ixodes hexagonus, 
I. ricinus, I. canisuga, Haemaphysalis leachi, H. punctata, Bermacentor 
reticulatus, D. occidentalis, Rhipicephalus appendicidatus, R. sanguineus, 
R. simus and Amhlyomma hehraeum. Here the tick attacks and feeds 
upon three successive hosts upon which at each stage (larva, nymph 
and adult) it remains attached for some days, or more, until it becomes 
replete and abandons the host. There are two breaks in the chain of 
parasitism between the larval and adult stages. 
Type If., represented by Rhipicephalus evertsi and Hyalomma 
aegyptium. Here the larva and nymph are parasitic upon one host and 
the adult attacks a second host. Whilst upon the first host there is a 
short interval (represented in the diagram by a fine white line traversing 
‘ Parasitology, in. 52-56, reprinted in Ticks, Part II, 330-334. 
