AY PRELIMINARY REPORT 'ON THE TROMBIDIIDAE, OF 
MINNESOTA? 
By C. W. Howarp? 
In the vicinity of Lake Minnetonka and other lakes near Minne- 
apolis and St. Paul, summer visitors are attacked by “chiggers,” 
similar to those found in the southern states, altho not so severe in their 
effectsonman. They are apparently the larvae of a mite belonging to the 
Trombidoidea. Several forms in this group are also of economic im- 
portance in being enemies of insect pests. Three years ago a study 
of these mites was begun, part of the work centering about an investi- 
gation of the life history and biology of the members of the family 
Trombidiidae, found in Minnesota. The purpose was to make a com- 
plete study of this family before publication. As it will be impossible 
for the writer to complete this study, and as our information about the 
representatives of the family in America is very incomplete and frag- 
mentary, the following descriptions and notes are presented at this 
time. Several apparently new species have been found in the state 
and these are also described. 
Those wishing more general information on the superfamily are re- 
ferred to Report 108, U. S. Dept of Agr., Office of the Secretary, by Nathan 
Banks, and to Redia, Vol. 8, No. 1, containing an account by Berlese of the 
trombidium mites of the world, but excluding North American forms almost 
entirely. 
KEY TO ADULTS AND NYMPHS FOUND IN MINNESOTA 
A. Palpi with a single claw. 
B. Dorsal grove expanded at the middle of its length. 
(Cc: A pulvillus between the tarsal claws; eyes truncate, a large 
species. Allothrombium pulvinus 
CC. No pulvillus, eyes sharp pointed, a small species; a white 
band across abdomen. Trombidium maculatum 
BB. Dorsal groove expanded at the anterior end. Abdomen deeply 
indented on the posterior margin. Sericothrombium scabrum 
AA. Palpi with two claws. 
183, A chitinous plate on the posterior part of the dorsum. 
Eutrombidium locustarum 
1 Published with the approval of the Director as Paper No. 140 of the Journal 
series of the Minnesota Agricultural Experiment Station. 
2In fairness to Mr. Howard, who has been in China since October, 1917, it should 
be stated that this paper has not been edited, corrected or revised by him.—A. G. R. 
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