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Zenoleum, crude carbolic acid, and official lime and sulphur dip showed 

 that in every case pupae hatched readily after one minute's immersion, 

 while adults were not killed by the last-named dip. Laboratory tests 

 were made with the following dips : Chloroleum 1 : 63, Carboleum 

 1 : 100, Cooper's Fluid Dip 1 : 150, Kreso 1 : 75, Chloro-naptholeum 

 1 : 50, Zenoleum 1 : 50, and 25 per cent, kerosene emulsion. Many 

 pupae hatched after being dipped in each of these, except those dipped in 

 kerosene, though 5 per cent, kerosene will not kill all the pupae, and a 

 higher percentage cannot be used on the host. Variations occurred 

 in the action of the same dip, indicating that certain physical or 

 chemico-physical factors were involved. In every instance but one, 

 the pupae of the controls began to hatch before those which had been 

 dipped. Tliis was probably due to the cooling action of the wet wool. 

 The controls continued to hatch for several days after hatching had 

 ceased among the dipped forms, showing that all the youngest pupae 

 were killed by the fluid. The experiments indicate that more than 

 one dipping must be made if the pest is to be eradicated. Since the 

 dips will not kill all the pupae, the last dipping must be done after 

 every pupa has hatched. In summer, the normal incubation period 

 is 23 days. Experiments carried out to determine the effect of dipping 

 on the duration of this period, showed that, if pupae were dipped before 

 they were four days old, they were killed. Pupae dipped after the 

 first four days usually hatched within 23 days. It is concluded that 

 the possible prolongation of the incubation period by the first dipping 

 need not be considered in determining when the last dipping should 

 be made. In another series of experiments, the following fluids 

 were found to be effective in destroying this parasite : Zenoleum, 

 Chloroleum, Chloro-Naptholeum, Kreso, Minor's Fluid, Betz's 

 Sanitary Fluid and Pyxol. Sanitary Fluid in the proportion 

 ] : 100 and Pyxol 1 : 200 were especially satisfactory. A detailed 

 account of the effect of the dipping fluids on the parasites is 

 given. With regard to the effects upon the sheep and wool, together 

 with the ease of preparation of the dip, very little distinction can be 

 drawn between the different coal-tar dips mentioned, except that 

 crude carbolic acid tends to blacken the wool and is difficult to prepare. 

 The cost of Cooper's Powder dip (an insoluble arsenical compound) 

 is about twice as great as that of coal-tar compounds, but its effect 

 on the parasite is similar and it has the advantage of remaining in the 

 wool for some months. It is suggested that a suitable dip would be 

 obtained by mixing Cooper's Powder with one of the coal-tar dips in 

 about one- half the strength recommended for use. From the data 

 obtained, it appears that at least three dippings about 14 days apart 

 are necessary to eradicate the parasite. This conclusion is based on 

 the fact that, in warm weather, the pupae require from 19 to 23 days 

 to hatch and a young individual may reach sexual maturity in 14 days. 

 Since dipping renders the conditions unfavourable, it is probable that 

 at least three weeks are required for the parasite, when dipped, to 

 reach sexual maturity. These theoretical results were supported 

 by actual tests. Early autumn seems to be most suitable for dipping. 

 •With regard to the question of compulsory dipping, the author is of 

 the opinion that M- ovinns would be eradicated in one year if the work 

 were systematically carried out and owners were compelled to dip 

 their flocks. 



