16 Confy^ol of the Greenhouse White Fhj 



'paeolum and also to a certain extent on Polygonum aviculare. This form 

 may be that originally described by Barensprung as com/planatum, but 

 his description is totally inadequate. It almost certainly is sonchi of 

 Kotinsky from Hawaii, and the absence of the two tiny caudal spines 

 would make it tentaculatus Bemis, from California. On P. aviculare 

 I find in my preparations both typical and atypical pupa cases, but on 

 the tomato the typical form seems to be present alone. Is it not possible 

 that the two forms were present at the beginning and that only the 

 typical form developed on the tomato? The case would then be very 

 similar to Morrill's experiment when he separated pacJcardi Morrill from 

 vaporariorum . In addition to the absence of the dorsal tubercles in the 

 atypical material there are other minor differences and seeing the material 

 without knowing anything of the experiment I should unhesitatingly 

 have called the two forms distinct species." 



It was intended to do further work with the atypical form in the 

 present summer but circumstances have prevented this. Its wide distri- 

 bution, Hawaii, Guernsey, the Lea Valley, and possibly CaUfornia, and 

 its apparent association in two of these with A. vajjorariormn make it 

 a very interesting form. 



7. ECONOMIC IMPORTANCE. 



Financial loss caused by A. vaporariorum results mainly through its 

 attacks on tomatoes, beans and potatoes grown under glass. The two 

 latter suffer less than the former because they are brief crops and the 

 insect does not have the same opportunity of causing massive infestations 

 on them for this reason. The damage is partly direct through loss of 

 sap, but is mainly due to the layer of honey dew which soon covers the 

 foliage and fruit of the infested plants. In this medium sooty moulds 

 grow, forming a black felt over the foliage which keeps away sunlight, 

 while all fruit from infested plants must be wiped before it can be 

 marketed. The fungus growth on the tomato plants was examined by 

 Dr W. F. Bewley, who found it to consist of Penicillium sp. predominating, 

 together with Cladosporium herbarum and Fumago vagans, all saprophytic 

 forms. 



In order to estimate the damage done by an unchecked attack on 

 tomatoes, 34 young plants in 12-inch pots were lightly infested with 

 about ten adults each on May 6 and placed in a chamber in the green- 

 house. On half of them the pest was allowed to develop unchecked while 

 the others were removed about once a fortnight to another chamber and 

 fumigated with hydrocyanic acid gas in order to keep the infestation 



