ARACHNIDA. 255 
. Family IXODID 2. 
This family includes the ticks proper, and the species are some of 
them large, and especially when gorged with blood, and the females with 
eggs are quite bulky. In some cases they reach a length of nearly half 
an inch. The common dog ticks will serve as a good illustration of the 
They are only semiparasitic, most species attaining some growth 
before attaching themselves to animals, and in many cases they move 
; 
. 
. 
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! 
group. 
to and from their hosts at will. 
The species of Argas, formerly included with the Gamasids, are now 
included in this group as a subfamily. 
EXPLANATION OF PLATE III. 
Rhynchoprium spinosum, dorsal Fig. 2d. Capitulum, dorsal view. 
Fig. 1. 
view. 2e. Maxille. 
la. Ventral view. 2f. Stigma. 
1b. Young, capitulum not redrawn. 2g. Female sexual orifice. 
1c. Fullsucked individual,capitulum 2h. Front foot. 
projected. 2i. Haller’s organ of hearing. 
id. Capitulum, dorsal view. Fig. 3. Argas americanus, dorsal view. 
le. Maxille. 3a. Ventral view. 
1f. Mandibles. 3b. Side view of anterior portion. 
1g. Stigma. 3c. Larva, dorsal view. 
ih. Front foot. 3d. Larva, ventral view. 
li. Haller’s organ of hearing. 3e. Capitulum, ventral view. 
Fig. 2. Ornithodorus americanus, dorsal 3f. Mandibles. 
view. 3g. Maxille. 
| 2a. Ventral view. dh. Stigma. 
2b. Side view of anterior portion. 3i. Front foot. 
. Position of capitulum in full- 
sucked individual. 
*, Haller’s organ. 
THE EAR MITE. 
(Sejus auris Leidy.) 
In 1872 Dr. Leidy, in the Proceedings of the Philadelphia Academy, 
described a mite from the ear of an ox, which he referred to the 
genus Gamasus, but Murray considers it a Sejus. It is evidently not 
| a common form, as [ find no further mention of it in American litera- 
ture and nothing to indicate an injurious attack from it. 
| * 
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: 
THE PIGEON TICK. 
(Argas reflerus Fab.) 
This is a common species in both the Old and New World, and 
occurs principally in the more southern latitudes, but in Europe extends 
