Gr. H. F. Nuttall 
73 
in immature ticks. Such ticks at any rate may run about on the host 
for some days before they attach themselves and proceed to feed. We 
have observed this especially with regard to Rhipicephalus bursa, 
regarding which I shall report in a future paper. This behaviour will 
account in some cases for the prolonged period which elapses before the 
ticks engorge and abandon the host. The shorter periods recorded for 
the stay upon the host are therefore more to be relied upon in deter¬ 
mining the period of parasitism. The seat of attachment of the tick 
upon the host may markedly influence the period of parasitism according 
to the blood supply of the host’s tissues at the spot where the tick 
introduces its mouth-parts. If the tick only imbibes serous fluid or 
lymph it may remain attached to the host considerably longer than 
when it sucks blood. 
The longevity observed in Ixodid ticks kept in corked tubes in the 
laboratory will certainly be found to exceed that under natural sur- 
Fig. 1. Apparatus used for counting the number of eggs laid by a tick. 
roundings. These observations nevertheless possess a certain value 
since they indicate that certain species are able to live for very con¬ 
siderable periods without food and that they have to be guarded 
against from this point of view in the practical work of eradicatioii. 
The number of eggs laid by individual females was determined by 
means of a simple little apparatus which I devised for the purpose and 
which is represented in Fig. 1, one quarter its natural size: is an 
ordinary piece of glass, B three strips of glass cemented upon A in the 
form of the letter U between the arms of which C, a strip of glass, slides 
readily backward and forward whilst closely applied toB. The stippled sur¬ 
face D represents a single layer of eggs spread upon the glass between 
the frame B and the glass strip C which has been pushed downward 
to the point where the layer of eggs completely covers the quadrangular 
stippled surface which, as adjusted in the figure, represents about 
