304 



HOUSEHOLD INSECTS 



after about a fortnight, during which time they change 

 their skins three times and undergo metamorphosis, 

 they begin to burrow themselves." There may be genera- 

 tion after generation of the mites on the host, and they 

 increase so fast that they soon number among the 

 thousands. The irritation continues to increase with 

 the increase in numbers. 



Injury and contagiousness. — Wherever the mites are 

 present they cause an intense irritation and the affected 



person scratches 

 the parts inces- 

 santly. The ir- 

 ritation is much 

 increased under 

 the influence of 

 heat and exer- 

 cise, and always 

 becomes espe- 

 cially intense 

 when the patient 

 goes to bed. 

 The affected parts become covered more or less with 

 grayish scales of skin and later papules and vesicles ap- 

 pear and the irritation increases. Often the galleries 

 of the mites may be seen as tiny whitish or grayish 

 streaks in the skin. The action of the parasite is both 

 mechanical and chemical. The places on the body that 

 are attacked by the parasite are so definite that one 

 should have no difficulty in diagnosing the disease. If 

 there is any doubt the mites can be found and examined. 

 Itch is highly contagious and is contracted through 

 personal contact, especially through contact of the hands. 



Fig. 105. — Burrows of the itch mite beneath 

 the skin, diagrammatic. 



