181 



Mally (C. W.). Finely-powdered Mercuric Chloride (Hg. CL,) for the 

 Destruction of the Argentine Ant, Iridomynnex humilis, Mayr. — 

 S. Aft: Jl. Sci., Cape Town, xiii, no. 11, July 1917, pp. 565-567. 



Good results against the Argentine ant, Iridomyrmex humilis, as a 

 household pest, have been obtained with a tape consisting of strips of 

 cotton cloth thoroughly soaked in a saturated solution of corrosive 

 sublimate and then dried. Its rei^ellent action is probably due to 

 minute sublimate crystals on the surface of the cloth coming into 

 contact with, sensitive tissue on the feet or antennae of the ants ; and 

 there is also the possibility that the insects may poison themselves in 

 attempting to clean their feet and antennae by drawing them through 

 the mouth. 



This having suggested to the author that the use of finely powdered 

 corrosive sublimate would yield even better results, the opening of a 

 nest near the base of a large oak tree was experimentally surrounded 

 with a half-inch barrier of the substance about an hour before sundown. 

 The results of this and many similar experiments show that the ants 

 become excited and confused before touching the powder, probably 

 owing to the presence of very fine particles in the air, with the result 

 that they attack and mutilate one another and refuse to cross the 

 barrier, while many are poisoned, probably in the attempt to clean 

 themselves. 



The poison is more active in sunlight than in the shade and retains 

 its effectiveness for as long as eight or nine months. Light rains carry 

 it into the soil, but on evaporation it is again deposited on the surface 

 in a finely crystalline condition. This suggests the possibility of 

 treating the foundations of buildings, either during construction or 

 afterwards, with corrosive sublimate in solution as a preventive against 

 the invasions of ants. 



Mally (C. W.). A Convenient Type of Hydrocyanic Acid Gas Gene- 

 rator for Fumigating Vineyards for the Destruction of the Mealy 

 Bug, Psendo"occus capensis, Brain. — S. Afr. Jl. Sci., Cape Town, 

 xiii, no. 11, July 1917, p. 621, 2 plates. 



The difficulty experienced in fumigating grape vines with hydro- 

 cyanic acid gas during the wanter season for the destruction of Pseudo- 

 coccus capensis (vine mealy bug), owing to the smallness of the space 

 to be treated within the long, low, narrow, oiled canvas covers used for 

 trellis or stump vine treatment, has necessitated the adoption of a new 

 form of generator. In this a solution of potassium cyanide is used 

 to combine with the acid, thus obviating the loss of time incurred in 

 weighing or measuring off small quantities of chemicals. It consists 

 of a cylindrical leaden chamber, the upper portion of which forms a 

 detachable lid pierced by small holes on opposite sides near the top, 

 into which are fixed a pair of vertical tubes, one for the acid, the other 

 for the cyanide solution. 



To charge it the lid is held upside down and the tubes are filled with 

 the proper amount of the liquids ; the body of the generator is then 

 inverted over it and pressed into position. When the gas-tight cover 

 is in position over the vine, the generator, still inverted, is placed 



