3210 



THE JOINTED ANIMALS 



creeping upon the mud or the leaves of aquatic plants. The larva adheres to vari- 

 ous water insects. The water mites (Hydrachnidce} have been described as Trom- 

 bidiidce that have adopted an exclusively aquatic life. They live in fresh-water 

 ponds and streams, where they may be seen swimming freely by means of vigorous 



strokes of their legs, which act like oars. In 

 the adult the body is generally more or less 

 spherical, and usually of a bright red or green 

 color. The males of one species (Atax globator) 

 have a curious blunt tail-like prolongation 

 from the hinder end of the abdomen. The 

 eggs are laid in the spring, in the stems of 

 water plants which are perforated for the pur- 

 pose, and the six-footed larvae when hatched 

 Right-hand figure, WATER MITE (Ata* *pi- attach themselves to water bugs (Nepa), or 



Z^<M),SEEN FROM BELOW; l,eft-hand figure, 



WATER SCORPION, INFESTED WITH A tax. water beetles (Ztytiscus) , by means of a large 



sucker on the front of the head. The abdomen 



then starts growing, the feet drop off, and the creature remains hanging like a sack 

 to its host. One species (A tax bonzi) lives in the shell of the fresh-water mussel, 

 while a few (Pontarachna} are marine. The next family {Halacaridce) contains 

 marine forms differing from the last in many important features; the mouth parts 

 being more united. In 

 addition to the pair of 

 eyes on the carapace, 

 there is an unpaired eye 

 upon the epistome. These 

 marine mites do not ap- 

 pear to swim like their 

 fresh- water allies, but 

 creep on the stems of sea- 

 weeds and zoophytes. 

 They may be obtained 

 either by dredging in deep 

 water or in rocky pools 

 upon the coast. Passing 

 on to the family Gamasidce, we find the stigmata placed far back in the body, fre- 

 quently at the sides of the thorax, above the legs of the third or fourth pair. The 

 beak is imperfectly developed, the palpi being foot-like and free, and the mandibles 

 pincer-like. There are no eyes; and the legs are adapted for walking or 

 running. The species figured (Gamasus coleoptratorum) may often be seen 

 in numbers attached to the lower side of dor beetles. Others live parasitically upon 

 bats and birds, one of the commonest being Dermanyssus avium, which infests 

 poultry, canaries, and other cage birds, whence they sometimes migrate to the per- 

 sons who have charge of them. Ceylon, Sumatra, and Mauritius are the habitat of 

 Holothyrus, in which the body is hard and horny, like that of a beetle, and of a shin- 

 ing chestnut color. 



i. BEETLE MITE, Gamasus coleoptratorum (much enlarged); 2. DOR 



BEETLE, INFESTED WITH GamaSUS. 



