THE CANADIAN ENTOMOLOGIST. 



LIFE-HISTORY OF THE SHEEP SCAB-MITE, PSOROPTES 



COMMUNIS. 



BV C. P. GILLETTE, FORT COLLINS, COLOUADO. 



I am not aware that the full life-history of this insect has been 

 published, though I shall not be surprised to learn that such is the case. 



In order to know how long a time should intervene between the first 

 and second dippings for the cure of scab, we must know the period of 

 incubation and also the entire time elapsing from the deposition of the 

 egg up to the time that the mite from that egg, if a female, may be itself 

 depositing eggs. These points were determined in a series of experi- 

 ments conducted by the writer one year ago and were reported in a local 

 l)aper, the " Fort Collins Courier," last spring. I took seventy-five eggs 

 from a lock of wool drawn from the back of a badly infested lamb, and, 

 after dividing them in two nearly equal lots, placed them at once on the 

 skin of the backs of two lambs that were not infested with the mites at 

 the time. In order to irritate the surface a little and better prepare it for 

 the little mites that would begin at once to hatch, a lock of wool was 

 drawn in each case from the particular spot where the eggs were placed. 



Mr. Ball, assistant in my department, made a careful examination of 

 these " cultures" once a day until the mites from the eggs were fully 

 grown and themselves laying eggs. 



At the first examination a few young mites were found, which was to 

 be expected, as a few eggs among so many would be about ready to 

 hatch. At the end of the fourth day all the eggs had hatched. 

 At the end of the ninth day a (cw individuals were found in copula ; 

 and on the eleventh day eggs were found. As it required four days for 

 the newly deposited eggs to hatch, the entire time elapsing from egg to 

 egg would be fourteen or fifteen days. 



As there would be eggs in all stages of incubation upon a sheep when 

 the latter is dipped for the cure of scab, I have set the limit of time for 

 the second dipping at not sooner than five days, and not later than ten 

 days after the first dipping. If the second dipping comes at a time out- 

 side this limit, there will probably be eggs upon the sheep again. 



AMERIA TEXANA, French. 



From a comparison with an example recently sent me by Mr. Harri- 

 son G. Dyar, from the Smithsonian Institution, I find that this is synony- 

 mous with Pagara simplex, Walker. Ameria texami will then be known 

 as a synonym. " Q. H. French, 



