76 THE HOUSE FLY DISEASE CARRIER 



family Trombidiidae, but the adult has not been reared 

 and is still unrecognized in Europe. Riley found these 

 harvest mites on house flies in Missouri, in some years 

 so abundantly, he says, that scarcely a fly could be 

 caught that was not infested with some of them cling- 

 ing tenaciously at the base of the wings. Later he suc- 

 ceeded in rearing the adult, and described it as Trom- 

 bidium muscarum. In recent years Oudemans has de- 

 scribed TrombidiuiJi inusca from larval mites found 

 on house flies in Holland. 



"All these forms are minute, six-legged, red mites, 

 which cling to the body of the fly and with their thread- 

 like mandibles suck up the juices of the host. They are 

 nearly related to the so-called 'red-bugs,' or 'chig- 

 gers,' of the Southern United States. When ready to 

 transform, they leave the fly and cast their skins, the 

 mature mite being a free-living, hairy, scarlet creature 

 about one and five-tenths mm. long. The adults are 

 usually found in the spring and early summer, while 

 the larvae are usually found in the autumn on house 

 flies and other insects. 



Mites of the genus Pigmeophorus, of the family 

 Tarsonemidae, have also been taken on house flies. 

 They cling to the abdomen of the fly, but it is not cer- 

 tain whether they feed on the insect or use it simply 

 as a means of transportation. The hypopus, or mi- 

 gratorial nymphal stage of several species of Tyro- 

 glyphus, has been found on house flies. This hypopus 

 attaches itself by means of suckers to the body of any 

 insect that may be convenient. The mites do not feed 



