153 



appear that arsenate is sli<>litly less than half as active as arseiiite ; 

 further it was found that the comparative scalding eh'ects of 

 arsenite and arsenate are not proportionate to their tick- 

 killing effects; the scalding eSect of the arsenate being 

 proportionately less. A second series of experiments to 

 determine the scalding effect of sodium arsenate show 

 tliat this poison when absorbed into the system in sufficient 

 quantities will cause death, but spraying experiments (the method 

 used by the author) are very unsatisfactory for detecting the 

 scalding effect of a dip. In the author's opinion undue import- 

 ance has been given to this question of deterioration of dips and 

 the desire on the part of the farmers to have their dips tested 

 at periodic intervals is a mistake and an unnecessary expense, 

 except in those cases in which a dip tank has been left for some 

 time without being used or when the tank has become flooded 

 with rain-water. 



Fuller (C). Fly Plagues. An Unusual Outbreak of Stoinoxyx 

 calcitrans following- Floods. — Agric. J I. Union of South 

 ■ Africa, V, June 1913, pp. 922-925. 



On the 22ud April 1913 reports were received in Ginginhlovo, 

 Zululand, enclosing specimens of *S'. calcitrans and stating that 

 this fly was causing ulcerous sores in the skin of pigs, oxen and 

 mules, disturbing the animals' rest and stopping their feeding. 

 The reports added that the flies had only been in evidence since 

 tlie floods. On the 2nd May a batch of S. calcitrans was received 

 from Transkei, where they were reported to be attacking horses, 

 mules, cattle and even sheep in places for a distance of roughly 

 30 miles inward from the coast; many cattle had been killed. In 

 order to obtain relief the animals were reported to have stampeded 

 into the sea and into rivers everywhere. The pest is said to have 

 been intolerable in the areas mentioned for more than a month 

 after the heavy rains experienced in March. Though the fly is 

 common enough in South Africa, this is the first record of such an 

 unusual outbreak; but similar cases have been observed and 

 studied in the United States, where they were also accompanied 

 by considerable loss of stock [see this Review, Ser. B. p. 96]. The 

 author says that the farmer can do little to help his cattle except 

 by giving them such direct protection as he can devise with the 

 means at his disposal. Repellent smears and sprays have often 

 been suggested, but experiment has shown that none of these 

 give more than temporary relief, and some of those recommended 

 have proved injurious to the animals. The best method of con- 

 trolling S. calcitrans is by thoroughly scattering manure which 

 contains straw and by avoiding the accumulation of decaying 

 hay and other vegetable refuse. Working animals can also be 

 protected by covers, and stall-fed stock by screening their 

 stables. In connection with the unusual outbreaks of Stoinoxys 

 calcitrans experienced elsewhere, it has generally been found that 

 epidemics of disease follow; thus, in red-water areas native and 

 immune cattle are attacked by the disease, which is attributed 

 to weakness and anaemia resulting from the attacks of the fly. 



