52 Adaptation of Ticks 
Both species, if they had active larvae, would labour under a consider¬ 
able disadvantage under these conditions and an enormous number of 
larvae would be lost in the dust or sand, and would die from desiccation. 
It may be noted that the females in captivity burrow and lay their 
eggs above them on or near the surface of sand. To overcome these 
conditions they must be provided with a thick integument to protect 
them against desiccation; they must possess mouth-parts capable of pene¬ 
trating a thick skin and of drawing blood rapidly; an increase in size and 
Figs. 1—8. Eggs of Isodoidea showing their relative size in some species belonging to 
difierent genera. Outlines drawn with a camera-lucida and reduced. The scale to 
the right = l mm. (Original. G.ilL del.): 
1. Ixodes hexagomts 57-5 x 450 /j,. 
2. Haemaphysalis punctata 570 x 380 fi. 
3. Hyalomma aegyptium 550 x 425 n. 
4. Bhipicephalus evertsi 550 x 400 fi. 
5. Boophihis decoloratus 625 x 400 fj.. 
6. Amblyomma hehraeum 625 x 525 fi. 
7. Argas persicus 625 x 575 y. 
8. Omithodorus mouhata 950 x 750 fi. 
strength will render them more capable of dealing with the dust 
problem. The larval stage is, therefore, inactive. The females lay 
larger eggs (and fewer) than any other ticks, so that they contain 
enough reserve upon which the nymphs may develop. The first stage 
nymphs are rapid feeders, and very resistant to drought and prolonged 
starvation, although somewhat less so than the later stages. 
Group 3. 0. megnini. 
Omithodorus megnini is quite aberrant in its habits, and appears 
highly specialized in its adaptation to a life of pai’asitism. As in 
Group 1, the larva attacks the host and remains attached thereto for 
about five days, by which time it is replete. It moults in situ, and 
re-attaches itself to the host for 35—98 days, or more, slowly growing 
in size and doubtless moulting as do the nymphs of other Argasidae. 
The larvae and nymphs are especially prone to attack the ears of their 
hosts. When replete, the nymphs abandon the host, crawl up several 
feet on posts, trees, or the like, and hide in chinks and crevices. After 
about seven days, in summer, the adults emerge, but they do not seek 
