152 



numbers of Agrotis tritici, the caterpillars of which they parasi- 

 tise. Musca domestica, which seldom was attracted by the 

 author's baits, appeared however iu enormous quantities, all 

 the outer parts of the house, the blinds and the linen covers of 

 the doors from the outside, being- covered by their excrement, 

 while in the stables they caused a constant buzzing. Stomoxys 

 calcitrans was also abundant usually settling on the outer walls 

 of the stables. Notwithstanding all this, there were practically 

 no flies in the rooms of the house, which the author attributes, not 

 only to the general cleanliness, but also to a special precaution 

 practised by the owner, who poured on the window-sills daily a 

 solution of white arsenic and sugar in water ; upon entering the 

 rooms the flies, in this dry waterless country, immediately settled 

 on the water and were poisoned. Sometimes the number of dead 

 flies on the windows was so great that they were collected and used 

 as food for the poultry, the latter never being injured by the 

 poison. In tlie open country, away from the house, the numbers 

 of M. domestica, in the total absence of their chief enemies, were 

 very great. 



Laws (H. E.). The Tick-killing Properties of Sodium Arsenate. — 

 Agric. Jl. Union of South Africa, v, June 1913, pp. 915-921. 



This is a continuation of a previous report [see this Revieiv, Ser. 

 B., p. 133] on the relative tick-killing properties of sodium arsenite 

 and arsenate. The previous work indicated that arsenate was about 

 half as active as arsenite, and this confirmed the opinion formed 

 by Brunnich in Australia. He and other observers found that 

 cattle dips, after standing for some time, deteriorated in strength 

 and that this deterioration was due to the oxidation of the arsenite 

 of soda to arsenate. Other observers have noticed that samples of 

 dip which contained little or no arsenate on arrival at the labora- 

 tory contained nothing but arsenate when left standing for about a 

 week. Williams, on examining the dip from a tank in regular 

 use once a week, found that very little change took place in the 

 dipping tank, but that if the dip was left standing in the 

 laboratory, in a few months the whole was converted into arsenate. 

 It would thus appear that to prevent the deterioration of the dip, 

 cattle should be put through it at frequent intervals. Fischer 

 has proved that the change is brought about by bacteria, and 

 that these cannot operate unless the tank is allowed to stand 

 undisturbed. The author discusses this question and says that 

 it now appears that the formation of arsenate and the consequent 

 reduction of the tick-killing effect of dips has been exaggerated, 

 that arsenate of soda is in itself a valuable tick-destroying agent, 

 and that there is very little diiference between the activity of 

 arsenate at 1 in 150 and arsenite at 1 in 300, but what difference 

 there is is in favour of arsenite. Details are given of two series 

 of experiments upon a number of cows lent for the purpose. 

 The first series showed that arsenite 1 in 300, with and without 

 emulsion, gave slightly better results than the arsenate 1 in 150 

 with emulsion, but they were not so good as those obtained with 

 i\riS,e2iatG 1 in 100 with and without emulsion ; thus it would 



