ORDER ACARINA: THE MITES 293 



Family Bdellidce : Snout-mites. Usually red in colour. Cephalo- 

 thorax distinctly delimited from the abdomen and bearing an eye, or 

 eyes, at its posterior angles. The chelicerse are more or less united to 

 form a " snout." The pedipalps are often long and elbowed. The legs 

 are long and slender. The Bdellida are predaceous, feeding on other 

 mites and on small insects of all sorts, and are undoubtedly useful 

 to man. 



Family Cheyletida. Tiny mites resembling Snout-mites, but distin- 

 guished by their massive, prehensile (cheliform or subcheliform) pedi- 

 palps. They are actively predaceous on other mites. 



Family MyobiidcB : Mouse-mites. Small white mites parasitic on 

 small mammals, particularly on mice. In some respects they resemble 

 itch-mites {Sarcoptida), but the legs end in claws, and in one genus 

 {Myobid) the first pair of legs are very short and thick and end in a great 

 hook, something like the tarsal claw of a crab-louse, for grasping hair. 



Family Hydrachnida. Aquatic mites, mostly living in fresh water, 

 though some are found in brackish and salt water. There is no distinc- 

 tion between cephalothorax and abdomen, and the legs are fringed with 

 long hairs, for swimming. The adults are predaceous on small aquatic 

 animals, including insect-larvas. The larvae are commonly parasitic on 

 aquatic animals, sometimes on mosquito-larvae. The larva has very 

 small appendages, and as it becomes distended with the juices of its host 

 it looks like an egg. 



Family Ualacaridce. Marine m'tes, with a distinct, movable head. 

 They crawl about on seaweeds and zoophytes, and are for the most part 

 carnivorous. 



Family OribatidcB. Mites with a hard, often dark-coloured, beetle- 

 like integument. The Cephalothorax, which carries the appendages, is 

 generally distinctly demarcated from the high, dome-like abdomen. 

 Near the posterior angle of the cephalothorax, on either side, there is a 

 pore, ox pseudostigma, out of which springs a stout, usually club-shaped 

 bristle. In one group the cephalothorax is movably articulated with the 

 abdomen so that the mite can roll itself up. The species of this family 

 are neither parasitic nor predaceous. 



Family Holothyreida. Mites as big as lady-birds, with a hard, 

 polished cuticle, a scutum covering the whole dorsum of the body, and 

 long legs. At present only known from certain Indo-Pacific Islands. 



Family Opiliocarida. This family includes a few species of long and 

 rather slender-legged mites in which the abdomen is composed of lo 

 distinct segments, each of the first 4 of which has a pair of dorsal 

 stigmata. According to Oudemans, it is still doubtful whether they 

 belong to the Acarina or not. Only three species are known, from North 

 Africa, Sicily, and Aden. 



