86 Habits of the Tomato Moth 



summarised in Table V. In the first column the Lea Valley is divided 

 up into areas, and the second gives the number of definite replies re- 

 ceived from these. The remaining columns show the average number 

 of years since: (1) tomatoes were first grown under glass; (2) the cater- 

 pillar was first seen in the houses; (3) it became a serious pest. 



There is no gradation in the numbers in the third column, the 

 industry having been established a considerable number of years 

 throughout the district. The numbers in the last two columns show a 

 distinct gradation, which bears a close relation to the relative positions 

 of the areas. The earliest records are at Enfield Highway. From here 

 it seems to have spread rapidly through the congested area of nurseries 

 which follows the main road through Freezywater to Waltham Cross. 

 The first records from the other localities are : Cheshunt 1908, Broxbourne 

 before 1911 (indefinite), Hoddesdon 1909, Ware 1914. In the more 

 outlying districts the earliest records are: Waltham Abbey 1906, 

 Sewardstone 1911, Chingford 1913: and to the west of Cheshunt, in the 

 Hammond Street and Flamstead End district, 1914. 



It has therefore spread like an epidemic disease. Where the nurseries 

 are congested it has moved rapidly, and where there is a gap it has 

 lingered. In places it has made sudden jumps, for which the basket 

 method of spread would account. 



The moths which commence the infestation in each nursery are 

 thus derived in some way from another nursery in which the pest is 

 already established. In congested areas it may be that they are the 

 actual moths which have escaped from infested houses, or they may be 

 the offspring of such. The efforts of the insects to escape are so per- 

 sistent that it is certain that a large proportion of those that emerge in 

 the houses must succeed in doing so. These will naturally breed on 

 suitable vegetation around the nursery, and as they are passing out in 

 April and May, before the moth normally flies in nature, there is ample 

 time for them to have a large or total second generation in the late 

 summer of a favourable year. In the immediate neighbourhood an 

 increase of the species will result from this which will readily encroach 

 on adjoining nurseries. Several species of common butterflies and moths 

 frequently blunder into the greenhouses and may be seen beating against 

 the panes in their efforts to escape again. The more plentiful the species 

 becomes the more likely are individuals to blunder in, and if it becomes 

 excessively common the entry of a few each year becomes a certainty, 

 since the total area of the ventilator openings is large. The escaping 

 moths would thus account for the increase and the consequent spread. 



