IXODID^. 661 



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

 Europe it is found on the linden tree. The young 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. 



Hydrachnid.e Sundeval. The Water-mites are known b}- 

 Imving the maxillary palpi five-jointed, with terminal hooks, or 

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

 hiudermost 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 young difter so much from the adults that they were de- 

 scribed b}^ Audouin under the name of Achlysia. In Hy- 

 dnickna 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 concharum is parasitic throughout life on the gills of 

 fresh water mussels. Others are parasitic during early 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. The 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, with the large 

 spatulate, dentate "glossoide" of the maxillse, 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 liatched young (Fig. 638, a, glossoide ; h, mandibles ; 

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

 the legs being very long, and the head and mouth-i)arts are 

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



