BIOLOGY AND CONTROL, OF CHIGGERS. 3 



the writer's attention, but some of the larvse are probably active 

 during this month. 



During the season of 1920 the chiggers were first noted in south- 

 eastern Iowa on June 24, when several attached themselves at Keo- 

 sauqua, where they were present in the State park. 



How chiggers pass the late fall and winter is not kn!Own, and will 

 not be known until more work is done on the life history of the 

 species and something is known of the nymphal and adult instars. 



LOCAL DISTRIBUTION. 



Investigations of the last year and a half have thrown much light 

 upon the local distribution of our chiggers, which in turn may fur- 

 nish the clue for locating their natural hosts and thereby give us 

 an opportunity to rear the larva? to maturity. 



Around Washington, D. C, the chiggers usually have been encoun- 

 tered where there was a heavy growth of wild brush or blackberries. 

 They are not found in cultivated fields or where the ground is bare 

 or in well-kept parks and lawns. Usually they are absent from 

 meadows and from weed patches unless some kind of growth of 

 canes or shrubbery is present. They are always encountered to some 

 extent in woodlands, but are present in great numbers only where 

 there is a considerable growth of underbrush. 



In the State of Iowa the chiggers have an even more interesting 

 distribution. Here whole counties in the northern part of the State 

 are apparently free from them notwithstanding that conditions for 

 them seem ideal. The writer has collected mites for years about 

 Ames, Iowa, and on many occasions has made special trips in search 

 of chiggers, but has never found a single specimen in this locality. 

 Yet the town of Ames is almost surrounded by woods and hemmed 

 in by two creeks, and there are situations almost exactly like those 

 along the lower Des Moines River, where chiggers are abundant. 



Judging from the records up to date, chiggers are only present 

 along the main river courses in the south-central, southeastern, and 

 eastern parts of Iowa. From the city of Des Moines north along 

 the Des Moines River the writer has not been able to collect speci- 

 mens, although the attempt was made in several localities. 



The environment found necessary in Iowa is the same as that in 

 Virginia or Maryland, since nearly all the land is given over to 

 cultivation; however, chiggers are found only in a relatively small 

 area, while in the East they are found over very extensive ones. 



HABITS OF UNATTACHED LARViE. 



The belief has been almost universal that chiggers in this country 

 are found in the grass. Observations have failed to confirm this 

 theory. It was found that our northeastern species occurs almost 



