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 weU 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. 



Class VII. Acarina (Mites). 



Chaeacteeistics. — Abdomen nmsegmenied aTid 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 Amrina. 



1. Chelioerae. 4. 2nd pair of walking-legs. 



2. Pedipalpi. 5. 3rd ,, ,, 



3. 1st pair of walking-legs. 6. 4tli „ ,, 



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 ^s ecto- 

 parasites. 



