138 



Griffitts (T. H. D.). Anopheles and Sea Water, with Observations 

 on the Influence o! SaUnity on the Development of American 

 Species. — Publie Health Repts., Washington, xxxvi, no. 18, 

 6th May 1921, pp. 990-1000'. 



The observations of various authors on mosquitos thriving in sea- 

 water are quoted, and the author's notes on Anopheles quadrimaculatus, 



A. crucians and A. pnnctipennis are given. It was found that 

 A. crucians can breed in diluted sea-water with a maximums ahnity 

 of 10,088, or slightly more than 50 per cent, average sea-water. 



A. quadrimaculatus may possibly withstand a higher salinity inter- 

 mittently, but was not found to breed in sufhcient numbers to be of 

 sanitary importance in a higher salinity than 10,003, or 1 -5 per cent, 

 sea-water. Individuals transferred from fresh pond water to water 

 with a sahnity of 10,160 were all killed within 12 hours. Although 



A. pnnctipennis breeds under a wider range of conditions than either 

 of the other two species, it apparently does not survive in salt or 

 brackish water, and larvae placed in sea-water all died within seven 

 hours. 



Theiler (Sir A.). African Horse Sickness [Pestis eqnorum). — Union 

 S. Africa Dept. Agric., Pretoria, Sci. Buh. 19, 1921, 32 pp. 

 [Received 21st June 1921.] 



Horse-sickness is a disease of equines caused by an ultra-visible virus 

 which is probably transmitted by a blood-sucking insect. It is notice- 

 able that this disease of horses frequently appears simultaneously with 

 malarial fever in man, especially in the low-lying regions of the Transvaal 

 and Natal. The area of distribution of the disease, however, is not 

 the same, horse-sickness occurring over a much wider area and 

 at much higher altitudes. Evidence definitely points to insect 

 transmission ; this is particularly demonstrated in the safety of horses 

 stabled in insect-proof premises. No proof has, however, as yet been 

 brought forward as to the identity of the insect that is the actual carrier; 

 Anophelines cannot be implicated for the reason indicated. Enzootic 

 outbreaks appear suddenly after heavy, prolonged rain, and many 

 deaths occur within a short time. The disease may appear in farms 

 or other places that are not well supplied with running or even standing 

 water, and cannot therefore be regarded as providing permanent 

 breeding-places for mosquitos. The transmitting insect must therefore 

 be one that does not require running water for its evolution and of 

 which the cycle is rapid, for the adults must appear very soon after 

 the rains. In fact, evidence shows that the insect must be able in 

 one stage of its development to maintain life without water. Obser- 

 vations over a number of years point to the possibility of some species 

 of Culicine, such as Ochlerotatus, being the vector. The larvae of 

 these mosquitos are found in hoof-holes, and the eggs can remain 

 alive in moist earth for a considerable time, while the life-cycle is com- 

 pleted in a week. The circumstances suggest that the adults emerge 

 infected, the infection having passed from adult to egg and having 

 survived through the subsequent stages. The question of where 

 the transmitting insects obtain the original infection has not been 

 definitely settled. The blood of a sick animal is infective and remains 

 so until some time after recovery, in some cases the blood of a recovered 

 horse when infused in large quantities into susceptible horses can 

 produce the disease. In one instance the blood of such a recovered 



