A cari. 
Ill 
to lay their eggs upon the ground, under stones, in grass, the crevices Table-case 
of walls, etc. The Ixcydidae are divided into two sub-families. N0, 26, 
Besides the specimens of Ixodidae exhibited in Case 26, a few 
specimens are on view in the North Hall. 
Sub-fam. — Argasinae. 
In the Argasinae the jaws are overlapped by a forward expan- 
sion of the body, and the skin is leathery and coriaceous ; the male 
and female are very similar in appearance (Genera : Argas and 
Ornithodoros). 
The Argasinae are chiefly parasitic on human beings, birds, 
and bats. The human tick-fever of 
tropical Africa (Spirillosis) is conveyed 
by the species known as Ornithodoros 
moubata ; the fowl-tick ( Argas Per- 
sians) is also known to transmit 
spirillosis amongst its hosts. 
Sub-fam. —Ixodinae . 
The mouth-parts of the Ixodinae 
are terminal. The skin is smooth ; 
a firm chitinous shield covers the 
whole of the back of the male, but 
leaves a considerable portion of that 
of the female uncovered. 
Several of the members of this 
Fig. 73. 
family are known to convey infectious Margaropus annulatus, the Cattle 
n . J , . , , Tick; distended female, x 5. 
diseases ; perhaps the most important (After Salmon and Stiles.) 
of these is the cattle-tick ( Margaropus 
annulatus ), a widely distributed form, which is the carrier of 
Texas-fever (Piroplasmosis). 
Sub-obdee IV.— PROSTIGMATA. 
Acari with a single pair of tracheal stigmata, which are situated 
on the anterior part of the body (except in the Halacaridae, in 
which the tracheae are absent). 
The Acari of this group differ greatly in their habits ; most of 
them are free-living and are found in moss, under stones, on 
plants, etc. They chiefly feed upon vegetable substances, but 
many of them prey on minute animals,. There are four families : 
Trombidiidae, Hydrachnidae, Halacaridae , and Bdellidae. 
