368 



Tortrix viridana, and the crop of acorns is expected to be poor. Vines 

 in Guadalajara are in excellent condition but are rather heavily 

 infested with Haltica ampelophaga, which is also present in the vine- 

 yards of Toledo ; arsenical mixtures are being appHed under the 

 direction of the Agronomical Department. Aelia rostrata is bemg 

 similarly dealt with in certain parts of Toledo where it has appeared. 

 In the Province of Madrid locusts have appeared in nimibers in many 

 locahties where the ground was left imbroken during the winter 

 campaign. The usual methods are now being followed for their 

 extermination. 



Les Parasites de la CochyIis-Eud6mis. — Le Progres Agric. et Vitic, 

 Motitpellier, Ixxiv, no. 24, 13th June 1920, pp. 565-566. 



Much discussion was raised some years ago as to the efficacy of the 

 artificial dissemination of fungus diseases among the vine moths [Clysia 

 ambiguella and Polychrosis botrana]. It was finally held that the 

 conditions necessary for this method of control, namely, moisture, 

 heat and prolonged contact of the insect with the spores, occurred 

 too rarely for the method to be of much practical value. The 

 author of the present paper has discovered that the larvae of 

 these moths are particularly susceptible, under favourable conditions, 

 to the muscardine disease of silkworms, Botrytis bassiana. Since the 

 life-cycle of the vine moths are similar to that of the silkworm, he 

 suggests that other infectious diseases attacking the latter insect, e.g., 

 pebrine, flacherie, etc., might be useful against the larvae of the vine 

 moths. 



PiCARD (F.). A propos de la Lutte contra la Cochylis et I'Eudemis 

 au moyen des Parasites. — Le Progres Agric. et Vitic., Montpellier, 

 Ixxiv, no. 25, 20th June 1920, pp. 589-593. 



In answer to the suggestion contained in the preceding paper, 

 a concise review is given of the position of natural enemies in 

 the control of insect pests, much of which has been written previously. 

 It is pointed out that the whole question is one of natural balance, 

 and that while much advantage may be gained by the introduction 

 from the country of its origin of the natural parasites of an imported 

 species, the artificial distribution of natural enemies against an 

 indigenous pest is a very different matter. In the former case the 

 natural balance has been upset by the estabhshment of a pest in new 

 surroundings where it is free from its natural enemies ; in the latter 

 case the mere fact of the balance being upset proves that conditions 

 are for the moment not favourable to the muItipHcation of the con- 

 trolhng factor, and therefore an attempt to introduce fresh individuals, 

 carefully reared in the laboratory, would be simply hke adding drops 

 to the ocean and would do nothing to remedy the existing unfavourable 

 conditions. Instances are given to illustrate these principles. 



In the case in question, there is nothing to gain by attempting to 

 propagate pebrine among vineyards infested with C. ambiguella and 

 P. botrana, as this disease already occurs in the locality among wild 

 bees and therefore, if it does not attack the vine pests, the reason 

 obviously is that the conditions are not favourable for its development 

 on them. 



