THE HABITAT OF PLA TYPA T'ROBUS DARLINGTON 
(COLEOPTERA: CARABIDAE) 
By Henri Goulet 
College Bourget, Rigaud, Quebec, Canada. 
Since its description in 1938, Platypatrobus lacustris Darlington has 
remained a great mystery. Despite intensive searches both in Canada 
and the United States, only six examples had been found. But in 
1965 the mystery seemingly was solved, for 51 specimens were cap- 
tured by the author and his companions during three visits to Meach 
Lake, Que., in Gatineau Park, near Ottawa. 
Platypatrobus lacustris was described as a new genus and a new 
species from a single female taken by Hubbard and Schwarz at 
Batchawana Bay, Ontario (north of Sault Sainte Marie) on August 
15, probably in 1876 or 1877. The species was known only from the 
type until Dr. C. H. Lindroth and Dr. P. J. Darlington discovered 
in the C. H. Frost collection a male taken at light by Dr. A. E. 
Brower at Sinclair, in northernmost Maine, on July 30, probably in 
the 1950’s. Br. A. Robert found another male at light in Mont 
Tremblant Park, Que., on July 1961. On July 28, 1963, two 
specimens were captured at light by Mr. and Mrs. R. T. Bell at 
Stowe, in northern Vermont. Finally Mr. J. Larson found one 
example on Simpson Island, in Great Slave Lake, N.W.T., Canada, 
on July 18, 1964; and found another example at light on July 28 at 
Lethbridge, Alberta, in 1965. 
The rarity of Platypatrobus indicates a special habitat. Dr. Dar- 
lington noted that, unlike species of allied genera, specimens of Platy- 
patrobus frequently bore mites and he suspected that these might offer 
a clue to the habitat of the beetle. Dr. E. Lindquist indentified the 
single mite carried by Mr. Larson’s specimen as Protodinychus sp. 
and pointed out that Protodinychus occurred commonly in beaver 
houses in Algonquin Provincial Park, Ontario (collector: Dr. M. 
Wood). 
At Meach Lake, Que., about 15 miles northwest of Ottawa, 
Ontario, the author discovered an abandoned beaver pond. The water 
level was very low and the beaver house was largely surrounded by 
very wet soil. On June 26, collecting very close to this house pro- 
duced one teneral specimen of Platypatrobus ; 40 specimens, including 
several that were teneral, were found on July 6, and 10 more on 
July 10. None were found on August 6, when the soil was less wet; 
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