DR. JOHNSTON ON THE ACARIDES OP BERWICKSHIRE. 223 



in August Then great numbers may be observed crawling 

 upon and over all green things, on turnips, grass, and corn ; 

 but certainly the object of their pilgrimage and quest is the 

 body of a living animal. 



This account of the " Harvest-bug" corresponds with what 

 we read of it in other authors. Gilbert White of Selborne 

 writes, — " There is an insect with us, especially on chalky dis- 

 tricts, which is very troublesome and teasing all the latter end 

 of the summer, getting into people's skins, especially those of 

 women and children, and raising tumours which itch intole- 

 rably. This animal (which we call an harvest-bug) is very 

 minute, scarce discernible to the naked eye, of a bright scar- 

 let colour, and of the genus of Acarus. They are to be met 

 with in gardens on kidney beans, or any legumens ; but pre- 

 vail only in the hot months of summer. Warreners, as some 

 have assured me, are much infested by them on chalky 

 downs ; where these insects swarm sometimes to so infinite 

 a degree as to discolour their nets, and to give them a red- 

 dish cast, while the men are so bitten as to be thrown into 

 fevers." 



Dr. Shaw tells us that our acarus is much smaller than a 

 common mite, and can but just be perceived upon the skin, 

 to which it adheres by its claws, and particularly by the two 

 short arms or tentacula, situated above the upper legs. 

 It can scarcely be separated from the skin when once it has 

 fixed itself; its motion when disengaged is considerably 

 quick,, though by no means equal to that of some other spe- 

 cies of acari. On the part where it fixes, it causes a tumor 

 generally about the size of a pea, sometimes much larger, 

 accompanied Avith severe itching. The colour is a bright 

 red, and, when microscopically examined, the lower part of 

 the body appears to be coated with stiff bristles. It seems 

 to be provided with a tubular snout, which is generally con- 

 cealed or sheathed, but which may sometimes be distinctly 

 seen. On the top of .the head are two little processes or 

 sharp implements, which turn outward each way. 



But is the Harvest-bug of Shaw identical with the Ber- 

 wickshire mite ? There can be no reasonable doubt of it, 

 from the sameness of their size, colour, structure, and habits. 



