666 ACARINA. 



states that during summer this mite is viviparous. T. farmce 

 DeGeer, as its name indicates, is found in flour. Other species 

 have been known to occur in ulcers. 



We figure the larva of the European Typlilodromus pyri 

 (Plate 13, fig. 4) the adult of which, according to A. Scheuten, 

 is allied to Tyroglyphus, and lives under the epidermis of the 

 leaves of the pear. There are but two pairs of legs present, 

 and the body is long, cylindrical and worm-like. Fig. 5, plate 

 13, represents the four-legged larva of another species of 

 Typhlodromus. 



The Itch mite belongs to the genus Sarcoptes^ in which the 

 body is rounded ovate, with needle-like mandibles, and with 

 short three-jointed legs. The female differs from the male in 

 having the two hinder pairs of legs only partially developed, 

 and ending in a long bristle. S. scabiei Linn. (Plate 13, fig. 

 7, female) was first recognized by an Arabian author of the 

 twelfth century as the cause of the disease wliich results from 

 its attacks. It buries itself in the skin on the more protected 

 parts of the bodj^, forming minute galleries, by which its pres- 

 ence is detected, and by its punctures maintains a constant 

 irritation. 



Other species are known to infest the cat, dog and swine. 

 They are best destroyed by the faithful use of sulphur oint- 

 ment. Various species of an allied genns, Dermatodectes, live 

 in galleries on different species of domestic animals ; thus D. 

 equi lives in the skin of the horse, D. bovis in cattle, and D. 

 ovis in sheep. Various Sarcoptids occur on birds ; among 

 them are species of Dermaleichus. On March 6th, Mr. C. 

 Cooke called my attention to certain female mites (Plate 13, 

 fig. 1) which were situated on the narrow groove between the 

 main stem of the barb and the outer edge of the barbules of 

 the feathers of the Downy "Woodpecker, and subsequentl}' we 

 found the other forms indicated in Plate 13, figs. 2 and 3, in 

 the down under the feathers. These long worm-like mites are 

 probably the females of the singular male Sarcoptes-like mite, 

 represented by Figs. 2 and 3 of the plate, as they were found 

 on the same specimen of woodpecker at about the same date. 



Tlie female (though there is probably a still earlier hexapo- 

 dous stage) of this Sarcoptid, which we may call Dermcdeichus 



