338 
Ornithodorus moubata 
minutes while a second only gained 0*0344 gram in 65 minutes. Whatever 
the extent of the meal 1 however, the period required for moulting was un¬ 
affected. 
The influence of moisture on vitality and ecdysis. 
0. moubata is said to prefer dryness. To determine the influence of 
moisture on metamorphosis, a lot of 150 first stage nymphs from the same 
female was divided into three, these batches being confined in covered jars 
and kept at 30° C. between meals. The atmosphere in the first jar was main¬ 
tained in a saturated condition by the presence of excess of water, to the 
second jar a very little moisture was added each morning and the air in the 
third jar was dried by means of a layer of calcium chloride. The first stage 
nymphs were fed on 18. ii. 1913 and each batch of the succeeding stages on 
16. iv. 13, 23. v. 13, 13. vi. 13 and 10. vii. 13 respectively. In the following 
table the minimum and maximum numbers of days required for ecdysis are 
given, with the mean in brackets and the number of individuals observed in 
square brackets: 
Atmosphere 
2nd ® 
3rd ® 
4th ® 
5th ® 
6th ® 
Saturated 
6—8 (6) 
6—15 (8) 
11 
— 
— 
[28] 
[22] 
[1] 
Moist 
5—8 (6) 
6—8 (7) 
8—11 (8) 
10 
— 
[40] 
[31] 
[20] 3 <? 
[6] 2c?, 3?,1® 
Dry 
5—6 (6) 
■oo 
1 
CD 
6—16 (7) 
7—14 (9) 
10—14 (12) 
[43] 
[36] 
[36] 3c? 
[32] 10c?, 14? 
[6] 2 
From these records it will be seen that an excess of moisture has no inhibitory 
influence on ecdysis (cp. Synopsis IV), but that it is decidedly unfavourable 
to the vitality of the individual, only one tick passing the third nymphal stage 
under these conditions. Even under medium conditions, the mortality was 
large only eight ticks maturing, whereas under dry conditions 66 per cent, of 
the nymphs completed metamorphosis. 
This result is of particular interest in relation to some observations of 
Rodhain (1919), on the distribution of O. moubata in tropical Africa. This 
author considers that the absence of the tick in the lower equatorial regions, 
in the very humid areas, may be partly, if not entirely, explained by the 
assumption that these ticks succumb rapidly, in a habitat of this character. 
Man, the normal host, may certainly be temporarily absent, but occasional 
hosts, such as warthogs, are frequently abundant. 
SECTION II. STRUCTURE OF O. MOUBATA . 
This section comprises notes on the dimensions of the egg and unfed 
specimens of the different stages, the changes in form undergone during 
development by structures of diagnostic value, namely the hvpostome, the 
fourth tarsus and the spiracle, and on the genital apertures of the two sexes. 
1 Forcible detachment, after partial engorgement, would no doubt affect the length of this 
period, or even prevent ecdysis if it occurred too early. 
