= BULLETIN 986, U. S. DEPARTMENT OF AGRICULTURE. 
exclusively at or near the surface of the soil. In this respect the 
larvee differ from tick larvae, which climb up on vegetation of various 
kinds and remain in wait a. a host. People frequently get chiggers 
when they go into the grass, but our eastern species approaches from 
the ground. The mites can be found in surface scrapings, but re- 
peated attempts to recover them from growing vegetation have 
failed.? 
if chiggers attack man almost solely from the ground the question 
may be asked, How are we to account for snc around the 
waist, under the armpits, and about the eyes? Again, observations 
show that chigger attacks are seldom made above the waistline, 
unless the clothes are quite loose around the waist, or the individual 
has been sitting or reclining on the ground. When one simply walks 
through a chigger-infested region, the larve are first found about 
the feet and ankles. Here they can be seen with a hand lens. They 
run with great rapidity, so fast in fact that it is very hard to catch 
them. From the ankles they spread upward, few as a rule attaching 
here, unless the clothing is tight; if so, many may attach. As they 
pass upward many of the larve either stop themselves or are stopped 
at the garters, if these are worn below the knees. If they pass the 
garters large numbers will attach in the space under the knees. 
Those that pass the knees usually go as far as the waistline before 
they attach. 
Two factors are of importance in regard to the localization of 
chigger attachment—the tightness of the clothing at certain parts of 
the body-and the thickness of the skin. The garters around the legs 
and the belt around the waist act as semieffective barriers. For a 
great many minutes, sometimes for a few hours, the larve run over 
the skin hunting a favorable place of attachment. These rapidly 
moving larve are halted by the garter or belt pressure, and aiter 
popes ae some time either to pass through the mesh of the clothing 
at these points or to extricate themselves may attach without cathe 
search. The writer has watched these active larve on the skin of 
man before and after attachment and finds that tight clothing does 
not aid them in “digging in” by furnishing a fulcrum, as has been 
supposed. In fact, it was found experimentally that chiggers do not 
“dig in,” as has been so frequently stated, but remain attached ex- 
ternally like a tick does. 
The thickness of the skin is of great importance in localizing chig- 
ger attachments. Where the skin is unusually thick the larve 
attach with great difficulty or not-at all; and of those that do attach 
2Dr. F. H. Chittenden has reported to the writer chigger attacks coming from over- 
head vegetation. ‘The writer has never experienced such attacks, and up to the time of 
the preparation of this paper none had been reported to him. It may be that a second- 
species, which is relatively rare, occurs in this yicinity, as Dr. Chittenden suggests. 
