302 



HOUSEHOLD INSECTS 



animal responsible for the trouble Acarus humanus sub- 

 cutaneus. Later, however, all of this knowledge concern- 

 ing the cause of itch seems to have been overlooked and 

 by many actually disputed and denied. During this 

 period the disease was variously attributed to " thickened 

 bile," "drying of the blood," "irritating salts," whatever 

 that meant, and other fantastic causes. Now, however, 



we know the life history, 

 appearance, and habits of 

 the tiny mite responsible for 

 the disease. In Figs. 103, 104 

 we show the male and female 

 mites as they look under a 

 microscope after they have 

 been removed from the skin. 

 Appearance of the mites. 

 — The itch mites are very 

 small — only just visible to 

 the eye as minute white 

 specks. It would take sixty 

 or seventy of the females and 

 eighty to one hundred of the 

 males placed end to end to 

 reach an inch. The body of each mite is oval and nearly 

 circular when viewed from above. The body is whitish 

 in color and when magnified is seen to be marked with 

 many fine transverse folds of the skin. There are four 

 pairs of legs situated in groups of two pairs, an anterior 

 and a posterior group. The anterior legs are usually the 

 larger and in both sexes each one terminates with a 

 sucker borne on a long pedicel. Each leg of the posterior 

 pairs in the female (Fig. 103) terminates in a long bristle, 



Fig. 103. — Itch mite, female. 

 (X85.) 



