105 



Hewitt (C. G.). Report of the Dominion Entomologist for the Year 

 ending March 31, 1916. — Dominion of Canada, Dept. Ayric. 

 Ottawa, 1917, 70 pp., 9 figs. [Received 31st May 1917.] 



In western Canada the red-tailed bot-fly, Gastrophilus haemorrhoi- 

 dalis, and the nose-fly, G. nasalis, were reported to be on the increase. 

 The warble-flies, Hypoderma bovis and H. lineatum, are also becoming 

 more widely spread and extending into new areas, owing to the 

 introduction of cattle from infested parts. In Manitoba blood- 

 sucking flies were unusually scarce, and mosquitos were practically 

 absent owing to lack of water for breeding-places, Tabanid flies being 

 scarce for the same reason. The stable-fly, Slomoxys calcitrans, during 

 1914 was a constant source of annoyance to cattle, horses and dogs, 

 but there was a great decrease in numbers in 1915 owing to the cold 

 wet w^eather in June. In Alberta, blood-sucking flies, especially 

 SiMULiiDAE, were very abundant and troublesome, especially near 

 running water, though their larvae were not found in the streams 

 examined and it is not known to what extent they breed in the large 

 rivers. Horses were attacked more than man and had to be protected 

 by ear-coverings and cloths when in harness, and by protecting the 

 pastures with smudges. 



As regards household insects, an endeavour has been made to 

 substitute the superheating method of eradication for bed-bugs for 

 that of fumigation with hydrocyanic acid gas, as being both cheaper 

 and safer. 



Bevan (L. E. W.). Immunity, in its Relation to the Stock Diseases of 

 Southern Rhodesia. — Rhodesia Agric. Jl., Salisbury, xiii, nos, 5 & 

 6, October & December 1916, pp. 640-651, 800-812, xiv, no. 2, 

 April 1917, pp. 213-229. 



In this series of articles the author reviews the principal diseases of 

 domestic animals caused by micro-organisms in Rhodesia. Among 

 diseases prevalent in Southern Rhodesia which are caused by Pro- 

 tozoan parasites are African coast fever, red-water, gall-sickness, 

 trypanosomiasis, biliary fever in equines and malaria in man. The 

 three methods by which parasites may bring about disease, i.e., by 

 mechanical efllects, by robbing the host of nutritive material, and by 

 the production of noxious substances, are discussed, and natural or 

 inherited immunity is contrasted with acquired immunity, either 

 active or passive. An important form of immunity occurs in Rhodesia 

 in which certain micro-parasites and their host live together in apparent 

 harmony, the host-animal being able to restrain the activity of the 

 parasite and to neutralise its injurious effects, or the parasite exhibiting 

 a period of non-infectivity. When the balance between host and 

 parasite is disturbed, the resistance to it may break down. An 

 instance of this is seen in the tolerance of game to trypanosomes, while 

 cattle from the north which are hurried through belts of Glossina may 

 remain apparently healthy for many months, but rapidly succumb 

 when exposed to the first rains, which often follow a period of drought 

 and scanty grazing. 



(C382) Wt.P5/131. 1,500. 8.17. B.&F,.Ltd. Gll/3. A 



