ENGLAND 389 



effective suppression of this pest. There is adequate reason for 

 beheving that the good results will be maintained after the 

 manner that prevails in connection with the two previously men- 

 tioned examples. The details of the campaign and the factors 

 involved are discussed at length in Taylor's well-illustrated 

 monograph, to which the reader is referred. It is thus evident 

 that the results achieved in Fiji rank among the most strikingly 

 successful examples of biological control under restricted or 

 islandic conditions. 



Experiments in England. (1) Encarsia formosa. Several 

 species of the Chalcid genus Encarsia are known to parasitise 

 Aleurodidse or " White-flies " in certain parts of the world, 

 including North America, the Orient, Africa and Barbados. The 

 first occurrence of a member of the genus in England was in 1914, 

 when a species, probably E. partenopea Masi, was noted by Fox 

 Wilson in a tomato house at Wisley (Surrey). In 1926 E. formosa 

 Gahan was found in a small greenhouse at Elstree (Herts.), and 

 an account of this insect is given by Speyer (1927, 1928). Its 

 country of origin is uncertain, but it appears to be a tropical 

 species, possibly imported on plants from India. It parasitises 

 the common white-fly Trialeurodes vaporariorum (Westw.), 

 attacking and destroying the pupae. Under suitable conditions 

 of temperature a number of generations can be bred under glass 

 each year, and stocks of the insect distributed among tomato 

 and cucumber houses have resulted in clearance of the white-fly 

 to an extent which rendered fumigation unnecessary. Owing to 

 its intolerance of cold, it is desirable to maintain the parasite in a 

 specially heated house over winter, so that large numbers are 

 available for distribution the following spring. The maintenance 

 and distribution of this parasite have been undertaken by the 

 Experimental and Research Station at Cheshunt (Herts.), and 

 the outlook for its utilisation as^ permanent measure appears to 

 be promising. (2) Aphelinus mali. The encouraging results 

 derived from the introduction of Aphelinus mali into New Zealand 

 and to a lesser degree in some other countries led J. C. F. Fryer, of 

 the Ministry of Agriculture, to explore its possibilities of controlling 

 the woolly aphis under English conditions. In 1923 colonies 



