280 THE CANADIAN ENTOMOLOGIST 



It is unquestionable that the isolation and perfect homogeneity 

 of the olive groves treated contributed to this remarkable success. 

 The authors emphasize the need of co-operation of olive growers . 

 in the same vicinity, so that a large area of olive trees may be 

 treated. 



The attack of Dacus upon olives results not only in the pre- 

 mature dropping of the fruit, but also causes a very serious dimi- 

 nution in the yield of the oil. Figures are given to show that in 

 order to produce the same quantity of oil, the ratio of olives re- 

 quired from untreated to treated trees is about 5-3. 



Dr. Cazeneuve (2) declares that mortal accidents have occured 

 with animals which have eaten sprayed olives or vegetation grow- 

 ing underneath or in the neighbourhood of treated trees. The 

 authors could not confirm any accidents of this kind. 



Can arsenic be found in the manufactured oil of olives obtained 

 from treated trees? Chemical tests by Gassend (2) of olive oil 

 obtained from olives taken from trees sprayed 2 or 3 days before 

 the crop was gathered showed traces of arsenic estimated at less 

 than .000001 gr. per liter. Negative results were obtained with the 

 oil when the normal interval elapsed between the last application 

 of the spray and the harvesting of the olives. 



The poisoned bait spray has some disadvantages. According 

 to Berlese, the spray stains the olives. The insecticide also stimu- 

 lates the development of fungi when a low per cent, of sugar is 

 present in the sweet substance, but in order to overcome this diffi- 

 culty, the bait ought to contain at least 30% sugar (glucose or 

 saccharose): According to the French scientists the fear of pro- 

 pagating fungi with heavy and numerous doses of the spray dis- 

 appears from the work of 1912. The small quantity of diluted 

 molasses is washed off with the first heavy rains. 



Dry Method. 



The dry method of controlling fruit flies consists in suspending 

 in the trees, a container holding the poisoned sweets in such a 

 way that the bait is constantly within the reach of the rapidly 

 flying fruit fly. This system would have the advantage of (l) 



