164 P>. C. Entomological Society 



THE RELATION OF THE PREDATORY MITE 



"HEMISARCOPTES MALUS" Shinier TO THE 



OYSTER-SHELL SCALE IN 



BRITISH COLUMBIA 



By E. p. Venables, Entomological Laboratory, Vernon, B. C. 



The careful researches of Dr. J. D. Tothill upon the distribution and 

 habits of this mite within the Dominion are recorded in Vol. 9 of the 

 Bulletin of Entomological Research for 1919. 



We find that during the year 1916-1917 samples of scale-infested 

 wood were received by liim from all the Provinces within the Dominion, 

 and were examined for the presence of this predatory mite ; whilst 

 occurring in all the fruit-growing sections east of the Rocky Mountains, 

 the mite was, for some reason, absent from the material sent in from 

 British Columbia. The samples from this Province were taken in the 

 following localities : Kaslo, Grand Forks, Vernon, Lillooet, Agassiz, Har- 

 rison, Nicomen, North Vancouver, Kuper Island, Victoria, Alberni, and 

 Duncan. 



As regards the presence of the mite within the North American 

 Continent, it is known to occur in Nova Scotia, New Bru^nswick, Quebec, 

 Prince Edward Island, Ontario, Massachusetts, Ohio, Illinois, and Iowa. 

 No examples were secured from the Prairie Provinces, this being prob- 

 ably due to the absence of suitable fpod plants for the Oyster .shell scale. 



From the very high destruction wrought by this mite among the 

 eggs of the scale in certain of these localities, reaching in some cases as 

 high as 90-95%, it became apparent that the introduction of the 

 Hemisarcoptes into the Province of British Columbia was a matter of 

 some moment, and to achieve this result the following method was 

 employed : 



Consignments of scale-infested twigs harbouring the mite were 

 secured from New Brunswick in 1917, and were placed upon trees in- 

 fested with Oyster Shell Scale at various points in the Province of British 

 Columbia as follows: Royal Oak (Brydon Farm), Mission (near Catch- 

 pole Farm), at Agassiz Experimental Farm, and at South Vernon. The 

 twigs as received were tied upon trees to be used as centres of distribu- 

 tion ; these included Hawthorne, Red Osier Dogwood, and Apple trees, 

 the Dogwood being found to be a ver.v favourite food plant attacked by 

 the scale. 



The trees selected for the liberation of the mite in the Vernon district 

 were situated some two miles from the city, and were growing on a piece 

 of waste land on the banks of the Vernon creek. These trees, three in 

 number, had been very heavily infested with the scale for some years, 

 and were growing in close proximity to the native timber fringing the 



