336 
Ornithodorus moubata 
equivalent adult stages, occupied more than ten days and a decrease in 
temperature of 8° C. did not double these periods. In Nature, an individual 
would require certain periods of quiescence to prepare and recover from 
ecdysis and very varying periods to enable it to find a suitable host. Ignoring 
these latter periods, the data given in Synopsis IV indicate that the mean 
minimum periods required for the metamorphosis of an individual from egg 
to adult are as follows: 
At 22° C.: S 64, 87 or 104 days. 
$ 84 or 103 „ 
At 30° C.: <? 36, 46 or 57 
$ 45, 55 or 72 „ 
according to whether the male undergoes four, five or six and the female five, 
six or seven moults. Therefore an increase in temperature of 8° C. (from 
22° C.) approximately halves the average time required for metamorphosis, 
and at the higher temperature there is more regularity in the individual 
life-histories. The adults emerge from the previous nymphal stage in the 
same time as the nymphs of the equivalent stage. 
The period of starvation appears to make but little difference in the time 
required after engorgement for ecdysis, provided of course it is not too pro¬ 
longed. Two batches of second stage nymphs, in one case, were starved for 
6 and 36 days respectively, yet the third stages emerged in mean periods of 
11 and 10 days; in another case, third stage nymphs starved for 5 and 18 days 
moulted in mean periods of 10 and 12 days; in a third case, fifth stage nymphs 
starved for 9 and 37 days produced females in 14 days. 
Preparatory to the emergence of a new stage, the nymphal skin normally 
splits laterally, as far as the ventro-anterior edge of the spiracle. The slit 
may not extend to the spiracle or it may go considerably beyond, a long 
series of specimens showing every variation. In all cases, however, the slit 
passes or tends to pass immediately under the ventral edge of the spiracle. 
The photographs 1 in Plate XVI show the successive stages of the emergence 
of the first nymph from the larval stage. In the first the larva is still partly 
enclosed in the egg-shell, in the second it is quiescent, with its legs contracted, 
preparatory to ecdysis. The first nymph then emerges, leaving its larval skin 
enclosed within the egg-shell, clearly shown in the last four photographs. The 
difference in texture between the larval skin and the egg-shell is very apparent. 
In many cases, however, the larva frees itself from the shell before under¬ 
going ecdysis, as in the case of O. savignyi. 
Duration and extent of engorgement at each stage. 
Engorgement can take, place at any stage of the life-history, after the 
larval stage has been passed, very shortly after emergence, probably as soon 
as the chitin of the mouthparts has hardened sufficiently to ensure penetra- 
1 These photographs were taken by the late Mr G. Merriman, from balsam preparations. 
