246 
MITES AND TICKS. 
specimens with benzine. A large number of mites living parasitically upon 
mammals—such as the mouse-mite ( Myocoptes )—and birds also belong to the 
Sarcoptidoe ; but the only species that we have space to mention is the itch-mite 
(Sarcoptes scabiei), which gives rise to the disease known as scabies. This 
malady and the irritation accompanying it are caused by 
the mite excavating tunnels under the skin. In these the 
eggs are laid, and hatch ; and the young then start burrow¬ 
ing on their own account. The burrows usually show as 
whitish lines on the surface of the skin, and if the skin at 
the end of one of these lines be pricked with a sharp 
needle, the mite may be without difficulty extracted. 
Worm-Like In the group Yermiformia the elongate 
Group. abdomen is divided into a multitude of small 
rings. There are no eyes and no tracheae. The suborder 
contain only the two families Demodicidce and JPhytoptidce. 
In the former the adult is provided with four pairs of short 
three-jointed legs; the mandibles are styliform, and the 
palpi formed of four segments, each armed with a claw. The family is represented 
by Demodex folliculorum, a minute mite less than J f) - of an inch in length, living 
parasitically in the sebaceous sacs and hair-follicles of the human skin. The 
same or an allied species has been found in the skin of a dog suffering from 
mange, where they occurred in such quantities that thirty or forty might be seen 
in a single drop of matter. The members 
of the second family, commonly known as 
gall-mites, have lost all trace of the third 
and fourth pairs of legs; the first and 
second pairs only remaining and projecting Demodex folliculorum (enlarged 600 times), 
from the forepart of the body. These legs 
are long and five-jointed, the mandibles are styliform, and the palpi tactile and 
united at the base. The long body is furnished with symmetrically arranged 
bristles. There are numbers of species, living exclusively upon the leaves of plants, 
to which they do much damage by the excrescences or galls they form. Each 
kind of tree seems to be infested by its own special gall-mite, the so-called nail- 
galls of the lime being caused by a species named Phytoptus til-ice. These galls 
take the form of more or less cylindrical pointed columns, which stand erect on the 
upper side of the leaves. As a matter of fact, they seem to arise as an inpushing 
of the lower surface of the leaf to form a long pouch or pocket, in which the mites 
live. Galls of much the same structure, although differing somewhat in shape, 
occur in the sycamore, maple, elm, and various fruit-trees. Other species, like 
the Phytoptus of the currant and the yew, attack the young buds and prevent 
them attaining maturity. 
The mites and ticks complete the list of Arachnida ; there remain, 
Aberrant Types. x . . 
however, two small and obscure groups, which have been associated 
with the ticks, but apparently for no better reason than that their affinities are 
unknown. The first of these are the Tardigrada, or bear-animalcules, which com¬ 
prise microscopical animals living in damp sandy and mossy spots. The body is long 
itch-mite (enlarged 80 times). 
(Lower view of female.) 
