244 
MITES AND TICKS. 
and the legs are adapted for walking or running. The species figured (Gamasus 
coleoptratomm) may often be seen in numbers attached to the lower side of dor- 
beetles. Others live parasitically upon bats and birds, one of the commonest 
being Dermanyssus avium, which infests poultry, canaries, and other cage-birds, 
whence they sometimes migrate to the persons who have charge of them. Ceylon, 
Sumatra, and Mauritius are the habitat of Holo- 
thyrus, in which the body is hard and horny, like 
that of a beetle, and of a shining chestnut colour. 
Of all the Acari the best known and most 
troublesome are those belonging to the family Ixodidce, 
which infest terrestrial vertebrates, and sometimes 
attach themselves to men. They are furnished with 
a longish cylindrical beak, armed with recurved 
hooks, and formed by the two mandibles above and 
the long slender labium below. The palpi are either 
free, as in Argas, or closely applied to the beak, 
forming in fact a sheath for it, and preventing the 
escape of blood, which flows from the puncture made 
by the beak. In the accompanying figure, showing 
the mouth - parts of the common English dog- or 
sheep-tick {Ixodes ricinus), the lower surface of the 
capitulum, or head-like process, which bears the beak 
. is shown at c; d, e, f, g, represent the four segments 
mouth-organs of sHEEr-ncK. Q £ p a ipj. y j s the labial process armed with the 
c , Capitulum; d, e,f g Segments of hooks f orming the lower side of the beak; and i 
fused mandibles. indicates the tips of the two mandibles, forming its 
upper side, and projecting beyond the apex of the 
labium. By means of this beak, which is thrust to its 
base into the integument, the tick adheres firmly to its 
host, and in detaching them care must be taken that the 
head be not left behind buried in the skin. The species 
I. ricinus is commonly found in all stages of growth (see 
a, b, c, d, e, f of figure) adhering to cattle. The females 
pump themselves full of blood, and swell up to the size of 
a large pea; but the male—formerly regarded as a distinct 
species under the name Reduvius —is of smaller size, and 
resembles the empty female in shape. In distribution 
these pests are almost cosmopolitan, but in tropical 
countries they reach much greater dimensions than in 
temperate climes, the females sometimes attaining the 
size of a large gooseberry. In addition to mammals, 
they attack birds, tortoises, snakes, and lizards; and even 
the thick hide of the hippopotamus and rhinoceros is of 
no avail against attack. On account of their numbers, 
the effects they produce upon cattle are sometimes of a 
serious nature. These ticks are not, however, found 
ENGLISH SHEEP-TICK. 
a, Six-legged young; b, Eight- 
legged young ; c, Male ; cl, 
Female not distended: e, 
Female, distended with blood 
from below; f, Same from 
above; g, Specimen clinging 
to the hairy integument of 
a mammal. (All figures en¬ 
larged twice.) 
