Ll. Lloyd 85 



and a dead male inside one of the screens on August 20. On the latter 

 date 16 of the jars were replaced by shallow dishes, 4 ins. in diameter, 

 filled with tanglefoot. These were placed at the tops of the calico sleeves 

 which were tied below to keep them in position. At the end of September 

 these traps were examined and four moths were found in them, three 

 being H. oleracea, two females and one male, and the other a common 

 Noctuid, Mamestra brassicae. It was thus proved that moths do pass 

 into the houses in infested nurseries, though the method failed to give 

 any estimate of the numbers of the invaders. The comparison of the 

 infestations of the screened and the unscreened parts of the block con- 

 firmed this. It was not possible to destroy entirely the first brood of 

 larvae, and some infestation was expected in all the houses from the 

 offspring of these. Very few larvae were found until July 25, when in 

 the two screened houses four mature ones were seen, and in two houses 

 in the unscreened part, four batches of newly-emerged and seven older 

 ones were found. On August 26 and September 10 an examination of 

 the two screened houses gave 12 batches of newly emerged larvae and 

 164 older ones, and at about the same time on an equal number of plants 

 in the unscreened part there were found 22 batches of newly-emerged 

 and 689 older ones. Judging by these figures there were in August more 

 moths to the house in the unscreened than in the screened part. 



Table V. Showing that the pest is a spreading one in the Lea Valley. 



Average No. of years since 



If it were a normal habit of this common moth deliberately to enter 

 glasshouses and to breed upon tomatoes all the nurseries should have 

 become infested soon after their institution, since it is very generally 

 distributed. The history of the pest in the Lea Valley shows that this 

 has not been the case. The growers have been questioned on the origin 

 of the pest in their particular nurseries and the answers received are 



