350
Life-history
of Boophilus australis
LARVAL STAGE
B. australis, being a continuous feeder, remains attached to the host even
while it undergoes metamorphosis, and hence it is easy to study the changes
which the tick undergoes during the entire course of its life-cycle, without
the employment of any special method for feeding and recovering the parasites.
The larvae were put on the back of the host and left there to seek a suitable
place for attachment. They scattered themselves and crawled excitedly over
the hair of the host, and most of them were found to be attached within ten
minutes. In selecting a site for attachment, they show a remarkable predilec-
tion for relatively soft and vascular parts of the body, such as the skin of the
neck, dewlap and escutcheon. Three days after attachment, the larvae change
their colour from dark red to reddish yellow, and experience has shown that
this may be regarded as an indication of the fact that the engorgement of the
parasites is complete and that they are about to undergo metamorphosis,
which they complete, as already mentioned, while remaining attached to the
host. From the fourth day onward, the colour gradually changes from reddish
yellow to dull white. This change commences at the abdomen and later
extends to the anterior end. On the seventh day, the change is complete and
the nymphs begin to emerge, leaving the larval skins attached to the body
of the host.
NYMPHAL STAGE
Immediately on emergence, the nymphs fix themselves to an adjacent
area on the skin and commence feeding. To start with they are of a dark
brown colour, and this gradually changes to dark grey by the fifth day, indicat-
ing that the nymphs have been fed to repletion. On the sixth day, the nym-
phs again show change of colour from dark grey to papery white. The change
commences at the hind end and gradually extends to the anterior. On the
seventh day, the nymphs begin to moult as adults, and by the ninth day all
the nymphs are found to have moulted. Thus it is seen that the nymphal
stage lasts from seven to nine days, the first four of which are spent in feeding
and the remainder in undergoing metamorphosis.
ADULT STAGE
The adults, like the nymphs, commence feeding immediately after the
moult, and select for this purpose a site adjacent to that to which they had
been attached in the nymphal stage. The males are invariably fewer in
number and, as is well known, also much smaller in size, than the females.
The male is almost always seen to fix itself near the female in such a manner
that their ventral surfaces are in apposition to one another. The male feeds
for one or two days and is then seen in copula with the nearest female. While
in this act, it clasps the female by means of its legs, and, as Sharif [1924] has
observed in the case of Hylomma ægyptium, the legs of the male are always
behind those of the female. On the sixth day, that is, shortly after fertiliza-
tion, a very noticeable increase occurs in the size of the female, which now
feeds and grows vigorously. Unfertilized females do not attain even half of
this size and do not, as a rule, lay eggs. From the ninth to the eleventh day,
the engorged females drop off to seek refuge in such cracks and crevices in the