BIOLOGY AND CONTROL OF CHIGGERS. 17 
It has been stated that the cropping or mowing of grass lets in 
more sunshine and in this manner destroys the chiggers. This can 
hardly be the case, however, as larve have been handled and exposed 
frequently in the bright sunshine and no ill effects to them noted. 
In the field also, where there is only a scant growth of dewberries and 
an abundance of sunshine chiggers may be found in great numbers. 
Chiggers are almost semiaquatic and will endure frequent sub- 
mergence. In the laboratory they do well, if not their best, in an 
atmosphere near saturation. This humidity requirement will help 
explain the advantage of a rough growth to the species, which lives 
almost exclusively at the surface of the ground. In most situations 
it may be that the moisture is only sufficient when the ground is 
clothed with a considerable growth of vegetation. Thus the effect 
of sunshine would appear to be indirect and to destroy the chiggers 
in most situations where allowed to act by drying the surface of the 
eround. | 
‘ DESTRUCTION OF THE CHIGGERS THEMSELVES. 
It is stated that chiggers may be destroyed by a hberal applica- 
tion of sulphur to the field. The use of 50 pounds to the acre has 
been recommended. For this purpose a dust gun or dust blower 
could be used to advantage. On lawns the use of sulphur is un- 
necessary, as chiggers will automatically disappear if the grass is 
kept cut short. 
Chiggers may best be destroyed on the body of man before they © 
become attached or very soon afterwards. If one knows that there 
has been exposure to chigger attacks the shins and ankles should be 
examined with a hand lens for the active larvee even before any itch- 
ing sensation is felt. Only a few of the active larve will be observed. 
They will be seen to run over the skin very rapidly and can not be 
captured to advantage. 
Larvee on the body can be easily killed by the application of an 
acaricide. Various substances applied at the time of bathing have 
been recommended. On August 10, 1919, after exposure to 
chigger attacks, a thick lather of soap was applied to the affected 
parts. The lather was allowed to remain for 10 minutes and was | 
worked continually over the skin. After 10 minutes it was washed 
off. Examination next day failed to reveal any chiggers and no 
itching developed. 
On August 18, 1919, after exposure at Somerset, Md., and after 
larvee had attached, the same application of thick soap lather was 
tried. On the 19th much itching was felt, yet no chiggers were 
found. Apparently the soap had acted as an acaricide but not as a 
palliative. 
