ORDER ACARINA: THE MITES 



287 



are characteristic. Many of them are predaceous on other 

 mites and on insects, some are parasitic on animals, and 

 some, such as the well-known " red-spiders," are very 

 destructive to plants. 



The larvae of Trombidiince may affix themselves to the 

 human skin, and when they are numerous, as they are at 



Fig. 126. — DerTrumyssus, from a Fowl. 



certain seasons, they will give rise to erythema and intolerable 

 itching. These larvae, which are known in all parts of the 

 world, and in Britain are called Harvest-mites, are micro- 

 scopic in size, round or oval in shape, red in colour, and have 

 three pairs of legs. They are produced in great numbers from 

 eggs which have been deposited by the parent on the ground. 



FiQ. 127.— Pedipalp of a Velvet-mite. 



The best treatment for this " autumnal erythema " is, if 

 the skin has not been very much broken by scratching, to 

 apply a compress or a bandage freely moistened with a 

 lotion of subacetate of lead, or perchloride of mercury, or 

 sulphate of copper. If this be not possible the part should 

 be painted with a mixture of Friar's Balsam (§j) and Menthol 

 (gr. xxx). Some recommend sulphur ointment. 



