10 
Elementary Manual of Zvology. 
legs attached to most of the segments of the body. They 
feed chiefly on vegetable matter. They have no poison 
claws and are quite harmless. The students should ex- 
amine and sketch a Centipede and a Millipede from the 
Museum collection and make out the structure of the legs 
and mouth parts in each ease. 
(c) Arachnida.—The Arachnida are a large group of air-breath- 
ing Arthropoda, which are characterised by the possession 
of four pairs of jointed legs. The only orders that need 
be noticed are the Acarina, the Araneida and the Scor-. 
pionidea, but it should be remembered that there are other 
orders which are equally distinct from each other (e.y., 
the Book-seorpions, the Pedipalpi and the Solfugez, some 
of which are represented in the collections of the School 
Museum). ; 
The Acarina (Mites) are mostly minute creatures. They have 
a thick-set body and unsegmented abdomen fused to 
the thorax. Their mouth parts are formed chiefly for 
biting and sucking. Many of the mites are parasitic 
ov plants and avimals, e.g., the so-called “ ved spider,” 
which attacks tea-bushes, and the itch mite of man. 
The ticks, which are common forest pests, are merely 
large mites. They are characterised by their strong 
dorsal shield and large protrusile toothed jaws. 
They usually pass their early stages amongst vegeta- 
tion, whence they crawl on to mammals and birds to 
suck blood. The efficacy of flowers of sulphur, either 
dusted on to the plants or sprayed in a mixture of soap 
and water, for destroying “ red spider” and other mites 
which attack plants, has been established. This form 
of treatment, however, is only practicable with valuable 
plants occupying restricted areas, as in the case of 
orange trees and tea-bushes upon which it has been 
successfully employed. A convenient mite for students 
to examine and sketch is the large red velvety Trombi- 
dium, numbers of which are preserved in the School 
Museum, 
The Araneida (Spiders) are characterised by their swollen 
unsegmented abdomen, which is separated off from the 
cephalothorax by a well-marked constriction. Most 
spiders have spinning glands situated at the posterior 
end of the body. The anterior pair of cephalic appen- 
dages (chelicerz) are formidable weapons furnished with 
poison glands, which aid in killing the insects on which 
