282 



The Sex of Eggs. 



[June, 



is so often recommended as a remedy for the onion fly, has 

 proved entirely inadequate. 



Heavy applications of nitrate of soda or of some similar stimu- 

 lant have been found in practice to prove very beneficial in 

 enabling the onion to withstand attacks by the onion maggot. 

 In recent experiments it was found that of two exactly similar 

 plots of onions, one of which was treated with nitrate and the 

 other left untreated, the former gave 64 lb. of clean onions as 

 compared with 32 lb. on the latter. 



Carrot Fly. — For the carrot fly (Psila rosae) remedies must 

 be applied early in the season when the carrots are a few inches 

 long and before the fly lays her eggs. The chief point of difference 

 between the life history of this insect and that of the onion and 

 cabbage root flies lies in the manner of egg-laying, the eggs being 

 deposited in the soil and not on the plant. Bearing this fact in 

 mind it will be seen that if the soil is dusted over with a thin 

 covering of chalk or earth impregnated with some insecticide, the 

 fly is likely to be deterred from egg-laying, while even if the egg 

 is laid, the tiny maggot may be killed by the chemical on its 

 journey from the egg to the carrot root. In practice it was 

 found that green tar oil, chlor-cresylic acid, or nitro-benzene, 

 gave the best results, when applied mixed with precipitated 

 chalk at the rate of J oz. of the chemical to 1J lb. of the chalk. 

 It should be mixed and applied as in the other cases. 



In captivity the carrot fly has shown a very great fondness for 

 sugar and will continue to feed upon it till the abdomen bursts 

 and the insect dies. It might be worth while in gardens and 

 allotments to put out a small quantity of syrup or molasses to 

 attract the flies away from the carrots. Whenever possible 

 carrots should be sown late, about the end of the first week in 

 May, as by this means the first generation of flies is avoided and 

 the risk of infection thereby lessened. 



Investigations into a means of increasing the proportion of 

 hens to cocks in hatchings were described in a communication 

 by M. Lienhart of the University of Nancy,* 

 The Sex of Eggs. made tQ the AoQi deime des Sciences in 1919. 



Starting from the facts that in the same breed cocks are 

 heavier than hens, that the weight of young male chickens is 

 higher than that of females, and that the same difference is 

 perceptible even in newly-hatched chicks, it occurred to Mr. 



9 See Journal d 'Agriculture Pratique, 14th Aug., 1919. 



