REPORT OF THE ENTOMOLOGIST 223 



SESSIONAL PAPER No. 16 



In most cases it would be more convenient and considerably safer to arrange for 

 Lie dropping of the cyanide into the sulphuric acid to be controlled from the outside. 

 This can be done as shown in the illustration. The cyanide wrapped up in thin paper 

 is suspended over the dilute sulphuric acid in the generating jar by means of a string. 

 Tin's string passes through a ring in the ceiling immediately over the jar and is con- 

 trolled through a small hole in the door. In this manner the cyanide may be lowered 

 into the generating jar after having sealed up the door. By the use of additional rings 

 and strings any number of jars may be used according to the size of the chamber to be 

 fumigated. In the case of large rooms, greenhouses and mills, where several jars are 

 required, this practice should always be followed. It is not advisable to use more than 

 1£ to 2 lbs. of cyanide to each jar. After the room or building has been ventilated care 

 should be taken in the disposal of the chemicals remaining in the generators which 

 should be most carefully cleaned out and the contents buried or thrown into a sewer. 

 Fumigation with hydrocyanic acid gas will kill the adults and larva) of many of the 

 insect pests, but it will not destroy the eggs nor all the chrysalids of the moths. In 

 order, therefore, to prevent a reinfestation by the hatching out of egg's or the emergence 

 of moths from the chrysalids which have survived the fumigating process, it will be 

 necessary to fumigate a second time about three weeks later. 



Some interesting experiments have been recently carried on by Prof. R. Har- 

 court* of the Ontario Agricultural College, Guelph, on the effect of mill fumigants on 

 flour and the results are of practical importance. Carbon bisulphide, which is some- 

 times used as a fumigating agent, has a very marked h:j; :::us effect on both wheat and 

 flour. It was found that bread made from flour which had been fumigated with carbon- 

 bisulphide in the usual proportions did not rise well and had a poor colour and tex- 

 ture. On the 1 other hand, fumigation with hydrocyanic acid gas did not affec-t in the 

 least the baking qualities of the flour, in fact, Prof. Harcourt stated, it would almost 

 seem to have improved the flour. 



INSECTS AFFECTING LIVE STOCK. 



In the western provinces, horses and cattle are affected to no small degree by 

 various species of biting flies, popularly known as ' Horse Flies ' or ' Gad Flies,' most 

 of which belong to the classes of two-winged flies known as the Tabanidae, and the 

 Uhrysopidae which include the smaller biting flies with banded wings. These insects 

 inflict very painful bites upon horses, cattle and other animals, including man. The 

 larva? are carnivorous and live in water or moist earth. Correspondents have asked if 

 there are no means of protecting horses, etc., from the bites of these and otber flies 

 such as the Black Flies (Simulium spp.). Many solutions having a repellant odourjiave 

 been used for this purpose with varying success. The chief difficulty is that the 

 repellent is not effective for long and when such repellents are used they must be 

 applied about twice a day. A solution of oil of tar has been found to be as effective as 

 most of the repellents and it is made as follows : — 



A quantity of coal tar is placed in the bottom of a large shallow receptacle and a 

 small quantity of oil of tar or oil of turpentine is stirred in. The vessel is then 

 filled with water which is left standing for several days until it is well impregnated 

 with the odour. The animals are then washed with this as often as may be deemed 

 necessary. 



the warble fly (Hypoderma lineata Villiers). 



Throughout Canada ' warbles ' occur on cattle. From reports received they 

 appear to be very abundant in the western provinces of Manitoba, Saskatch- 

 ewan and Alberta, and the losses which result from their occurrence are an 



* Thirty-sixth Annual Report of the Ontario Agricultural College and Experimental 

 Farm, 1910 (Toronto) pp. 87-92, 1911. 



