IXODID^. 661 



It may be killed by showering sulphur over the leaves. In 

 Europe it is found on the linden tree. The j'oung of this spe- 

 cies, according to Claparede, passes through an Ixodes-like 

 stage, as regards the mouth-parts, for this reason we place the 

 Ixodidce below them. 



IIydkachxid.e Sundeval. The Water-mites are known by 

 ]la^•ing the maxillary palpi five-jointed, with terminal hooks, or 

 bristles, at the end. The legs gradually increase in length, the 

 hindermost pair being longest ; they are ciliated, with two 

 claws. There are two ocelli. These mites swim in fresh and 

 sometimes salt water, and are seen running over water-plants. 

 The 3'Oung differ so much from the adults that they were de- 

 scribed by Audouin under the name of Achlysia. In Hy- 

 drachna the mandibles are needle-shaped, and the third joint 

 of the maxillae is the longest. The body is oval, with the 

 limbs adapted for swimming, and there are two eyes. Hy- 

 drachna conchariim is parasitic throughout life on the gills of 

 fresh water mussels. Others are parasitic during earl}' life on 

 fresh water Hemiptera and Coleoptera. 



In Atax the body is oval, solid and corneous. The mandi- 

 bles end in a stout curved claw, and the five-jointed maxillary 

 palpi end in an acute point. The species are red in color and 

 live in flowing streams ; when in their early, and in some cases 

 their adult stages, they are parasitic in the gills of mussels. 



IxoDiD^ Leach. Tlie Ticks are mites of gigantic size, with 

 bodies of a leathery consistence. The three to four-jointed 

 maxillae are small, not reaching beyond the beak. The man- 

 dibles are saw-like, being covered towards the end with teeth, 

 with from two to four terminal hooks, and, Avith the largo 

 spatulate, dentate "glossoide" of the maxillae, form a beak 

 which the tick pushes into the skin of its host. The ocelli are 

 often wanting, and the legs are slender, with two claws, 

 and in the young a distinct membranous foot-pad. The 

 recently hatched young (Fig. 638, a, glossoide ; 6, mandibles : 

 c, maxillary palpi ; e, adult gorged with blood) is six-footed, 

 the legs being very long, and the head and month-parts are 

 much larger in proportion to the rest of the body than in the 



