TRACHEATA 419 
ovary and testis are in the form of ring-shaped glands; the 
ova are said to be fertilised in the ovary. The testes some- 
times produce ova as well as spermatozoa. The female is 
provided with a large ovipositor, and the male with a large 
penis ; both of these structures are usually retracted within 
a sac. 
The females lay their eggs under stones or in crevices in 
the ground during the autumn; the adults of both sexes then 
die, so that until the eggs hatch out in the following spring no 
Phalangid is to be seen. They are largely nocturnal in their 
habits, and feed on small insects, spiders, etc., but at times 
they are cannibal. Their long thin legs enable them to run 
over grass and hay, and to steal with a “gliding spring” upon 
their prey. There are about twenty-four species found in 
Britain. 
Cuass VII. Acarina (Mites). 
CHARACTERISTICS.—Abdomen unsegmented and fused with thorax. 
The oral appendages are adapted for piercing, sucking, or 
biting. Tracheae usually present. 
The mites comprise an immense number of species, which 
vary greatly both in appearance and in habits; as a rule they 
are minute in size with stout roundish bodies. Many of them 
are parasitic on either plants or animals, others live on cheese, 
etc., and some are predaceous. 
Appendages of Acarina. 
1, Chelicerae. 4, 2nd pair of walking-legs, 
2. Pedipalpi. 5. 3rd a ss 
3. Ist pair of walking-legs. 6. 4th 56 a 
The chelicerae are clawed or chelate, or they may form 
piercing stylets, in which case they are protected by a sheath 
formed by the base of the pedipalpi. The rest of the pedi- 
palpus projects as a tactile palp, or may be clawed. The four 
pairs of legs vary in different species, they usually end in a 
pair of claws, but these may be replaced by a sucking-disk. 
The claws are often wonderfully adapted to fit round the 
hairs of animals upon which the mites may be living as ecto- 
parasites, 
