CHAP, xvm HARVEST-BUGS TICKS 455 



its identity. It was described as a separate species under the 

 name of Leptus autumnalis, and Megnin was the first to show 

 that it was the larval form of one of the Trombidiidae (see p. 

 472). Most authors have considered it the larva of Trombidium 

 holosericeum, but Murray referred it to the genus Tetranychus. 

 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 T. 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-grow T er, 

 too, has to take cognisance of the Order, for his trees may suffer 

 from " Eed-spider " (Tetranychus telarius), and his black-currant 

 bushes fail under the attack of the " Gall-mite " (Eriophyes 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, etc., see p. 466). One curious genus, 

 Syrinyophilus, 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 IXODOIDEA (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 likely 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 



1 C. -ft. Ac. Sci. cxxv., 1897, p. 879. 



