BIOLOGY AND CONTROL OF CHIGGERS. 5 
many can not remain attached during the body movements of the 
host or are not able to reach the lymph supply of the true skin and 
engorge. Of the thousands of chigger attachmcnts observed by the 
writer, not a single one was found on the calloused parts of the 
hands or feet. 
HOSTS. 
It was the belief of earlier entomologists that chiggers lived upon 
the juices of plants. That C. V. Riley shared this common belief is 
evident from the following statement (/0) which he made in regard 
to one of his species: 
The normal food * * * must, apparently, consist of the juices of plants 
and the love of blood proves ruinous to those individuals who get a chance to 
indulge it. 
When it was learned by actual rearing experiments that several of 
the species of Trombidiidae were normally parasitic on terrestrial 
tracheates, this older theory was dropped, and it was commonly as- 
sumed, and frequently stated, that the chigger larvae were normally 
parasitic on insects and dlosale related invertebrates. This belief 
was equally shared by the mite specialist and the general ento- 
mologist; but that the chigger larve could be normally parasitic on 
vertebrates was never suspected; in fact, the references to their 
“death feast’? on man or domestic animals continued as numerous 
as before. 
When the writer began, in the summer of 1919, his search for the 
natural host of the species occurring in Virginia and Maryland, he 
collected all insects found parasitized with trombidiid larve. ‘These 
larvee were examined to see if any of them belonged to the species 
attacking man, or were in fact true chiggers. Although many in- 
sects and other tracheates were found parasitized, in no instance did 
these parasitic larve prove to be the species attacking man. 
Not satisfied with this method of investigation, another was in- 
-stituted. On some vacant lots that had grown up to a considerable 
extent in blackberries and which were very heavily infested with 
chiggers (over a hundred attached in less than two hours), insects of 
all kinds were collected. There were hundreds of them and scores 
of species. 
These insects were taken to the laboratory and examined both 
alive and after killing in cyanide bottles, and in no case was a 
single specimen of our eastern chigger found. The sweepings and 
other collections were so thorough that this observation convinced 
the writer that the chigger found in the vicinity of Washington is 
not a normal Bae on terrestrial tracheates that live above the 
ground. 
