330 Appendix II [52] 



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 



12 3 4 5 6 7 



Fig. 289 [1-8]. Eggs of Ixodoidea showing their relative size in some species belonging 

 to different genera. Outlines drawn with a camera-lucida and reduced. The scale 

 to the right = 1 mm. (Original. G. M. del.) : 



1. Ixodes hexagonus 575x450/*. 5. Boophilus decoloratus 625 x 400 ix. 



2. Hdemaphysalis punctata 570 x 380 /x. 6. Amblyomma hebraeum 625 x 525 /*. 



3. Hyalomma aegyptium 550 x 425 p. 7. Argas persicus 625 x 575 /x. 



4. Rhipicephalus evertsi 550 x 400 ix. 8. Ornithodorus moubata 950 x 750 /*. 



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. 



Ornithodorus megnini is quite aberrant in its habits, and appears 

 highly specialized in its adaptation to a life of parasitism. 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 



