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UNITED STATES 
DEPARTMENT or AGRICULTUR 2h 
DEPARTMENT CIRCULAR 294 
Washington, D. C. October, 1923 
THE RAT MITE ATTACKING MAN. 
F. C. BISHOPP, 
Entomologist, Bureau of Entomology. 
The blood-sucking mite of the rat, Liponyssus bacoti Hirst, has 
recently attracted attention in the South as an annoyer of man. So 
far as the writer is aware there are no published references to the 
occurrence of this pest in the United States, although its habit of 
attacking man has been reported by Hirst. The species is known 
to occur in New South Wales and Western Australia, Egypt, Abys- 
sinia, and Argentina. 
The first occurrence of these mites in the United States to be re- 
ported to the writer was during the spring of 1920, when a depart- 
ment store in Dallas, Tex., called for aid. Early in 1921, reports 
of similar trouble began coming in from various establishments in 
Dallas and Fort Worth, Tex. The trouble in some instances was 
- acute, causing the expenditure of much time and money in efforts 
to combat it and, in certain cases, compelling the abandonment of 
parts of buildings, as in the case of the dead letter division of the 
_ post office'in the basement of the Federal building in Fort Worth. 
Dr. A. H. Flickwir, health officer of Houston, Tex., has reported 
_the occurrence of a mite attacking man in a building i in that city. 
Although the species was not determined, it is almost certainl y 
_ Liponyssus bacoti. = 
A similar occurrence of these mites has been reported by D. L. 
Van Dine. In this instance the trouble, which occurred in a rail- 
4 way station in a small town in Mississippi, was traced by Mr. Van 
Dine to the presence of many rats. 
OBSERVATIONS ON THE SITUATION IN TEXAS. 
The initial outbreak of this mite as a pest to man was coincident 
_ with a tremendous increase in the number of rats in the city of 
' Dallas. These rodents began to appear in unusual numbers in 1920 
and seemed to reach their maximum abundance in the early summer 
_ of 1921. Buildings which were newly constructed of steel and con- 
_ crete were overrun, and residences in which a rat had never been 
seen before were frequently invaded. 
1 Hirst, S. 1914. Bul. Ent. Research, London. Vol. 5, part 3, pp. 225-229, De 
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