

A CHAPTER ON MITES. 369 
the tripartite palpi, which are divided into an outer, long, 
curved, clawlike lobe, with two rounded teeth at the base, 
and two inner, slender lobes pectinated on the inner side, 
the third innermost lobe being minute. The beak termi- 
nates in a sharp blade-like point. 
We will now give a hasty glance at the different groups 
of mites, pausing to note those most interesting from their 
habits or relation to man. 
he most highly organized mite (and by its structure 
most closely allied to the spider) is the little red garden 
mite, belonging to the genus Trombidium, to which the 
genus Tetranychus is also nearly related. Our own spe- 
cies of the former genus have not been “worked up,” or in 
other words identified and described, so that whether the 
European T. holosericeum Linn. is our species or not, we 
cannot tell. The larve of this and similar species are 
known in Europe to live parasitically upon Harvest-men 
(Phalangium), often called Daddy-long-legs; and upon 
Aphides and other insects. The European Tetranychus 
telarius Linn., or web-making mite, spins large webs on 
the leaves of the linden tree. Then succeed in the natu- 
ral order the water mites, Hydrachna, which may be seen 
running over submerged sticks and on plants, mostly in 
fresh water, and rarely on the borders of the sea. The 
young, after leaving the eggs, differ remarkably from the 
adults, so as to have been referred to a distinct genus (Ach- 
lysia) by the great French naturalist, Audouin. They live 
as parasites on various water insects, such as Dytiscus, Nepa 
and Hydrometra, and when mature live free in the water, 
though Von Baer observed an adult Hydrachna concharum 
living parasitically on the gills of the fresh-water mussel, 
on. The species are of minute size. 
Collectors of beetles often meet with a species of Uro- 
poda attached firmly to their specimens of dung-inhabiting 
or carrion beetles. It is a smoothly polished, round, flat- 
tened mite, with short, thick legs, scarcely reaching beyond 
` AMER. NATURALIST, VOL. mL 
