CHAP, XVIII HARVEST-BUGS AMKGIEES 455 
its identity. It was described as a separate species under the 
name of Leptus autumnalis, and Mégnin was the first to show 
that 16 was the larval form of one of the Trombidiidae (see p. 
472). Most authors have considered it the larva of 7rombidium 
holosericewm, but Murray referred it to the genus Zetranychus. 
The difficulty is that the minute creature cannot be removed 
from its victim without such injury as to prevent it from being 
bred out and the mature form determined. Brucker ' has recently 
compared a large number of “ Harvest-bugs” taken from human 
beings with the figures and descriptions of the larvae of certain 
Trombidiidae given by Henking and Berlese, and he determined 
them as the larvae of 7. gynopterorum. Quite possibly, however, 
more than one genus is concerned in the production of this pest. 
That certain skin-diseases are due to Mites (Demodicidae, 
Sarcoptidae) is a fact which is widely known. ‘The fruit-grower, 
too, has to take cognisance of the Order, for his trees may suffer 
from * Red-spider” (Tetranychus telarius), and his black-currant 
bushes fail under the attack of the “Gall-mite” (Hriophyes or 
Phytoptus ribis). The curious swellings or galls which disfigure 
the leaves of many trees are sometimes of insect origin, but they 
are often due to Mites. 
Domestic pets suffer greatly from Acarine parasites. <A large 
number of species confine their attention exclusively to the 
feathers of birds (Analges, ete., see p. 466). One curious genus, 
Syringophilus, is parasitic within the feathers, feeding upon the 
pith of the quill. Heller of Kiel discovered them in 1879, but 
the researches of Trouessart first showed their frequent presence 
and very wide distribution. He found that they entered by 
the superior umbilicus of the feather, and disappeared by the 
inferior umbilicus when the feathers moulted or the infested 
bird died. 
It is probable that the comparatively large Mites of the 
group LYODOIDEA (see p. 468), commonly called “ Ticks,” are the 
most widely known of the order. They attack wild and domestic 
animals and man, and are nearly always acquired from vegetables, 
such as brush or herbage. It would seem lkely that many of 
these creatures can never have the chance of attaching themselves 
to animals, and it has been suggested that animal juices are a 
luxury but not a necessity to them, and that they can live, if 
LC, Re Ae. Sci. exxv., 1897 -p. 879: 
