Ll. Lloyd 97 



It was thus proved, by methods quite applicable to trade conditions 

 that moth trapping combined with poisoning, is a most useful method 

 of control. The experiment by itself showed that the danger of drawing 

 moths into the houses is negligible, but as there is a confirmed im- 

 pression that this risk is serious the matter will be discussed a little 

 further. The probable reason why this idea arose is that the growers 

 had no conception of the very large numbers of moths which exist in 

 the infested houses, and so, when they exposed baits, they could account 

 for the numbers trapped in no way except by assuming that moths were 

 being attracted in. 



If Hadena oleracea was drawn into the houses other common species 

 of moths, which are attracted to these baits, should enter also. Only 

 five individuals, other than this species, were noticed in the traps, and 

 two of these strange moths, Tryphaena pronuba and Xylophasia polyodon, 

 have been seen in houses where baits were not exposed. One of the 

 baited jars was placed in a tomato house in such a way that it communi- 

 cated only with the outside, by means of a calico sleeve and wide wire mesh 

 cone. Moths from outside alone could thus get into it (see PI. X, fig. 6). 

 It was exposed from June 20 to the end of the season, the bait being 

 renewed monthly. Only one moth, a male H. oleracea, was taken in it. 

 Finally, even if a few moths were drawn in, they would be trapped or 

 poisoned. 



In order to determine how many traps should be used the arrange- 

 ment in a block of 200-foot houses was varied. In the end house 12 were 

 placed, and in the adjoining houses in succession, 8, 6, 4, 3, 3. They 

 were left for five nights, and after the removal of the moths, were placed 

 in the remaining six houses of the block in the same succession, the end 

 house again receiving 12. After five more nights the moths were again 

 removed and counted. The total numbers caught were as follows: 



Number of traps ... 12 8 6 4 3 3 



Moths caught ... 47 35 42 22 20 36 



The last set of traps communicated on one side with houses in which 

 at this time there were none, and it should be noted that they took less 

 than double the number of moths taken by the three in the next house 

 which were surrounded by other traps. The houses were 22 feet wide, 

 so that the traps would appear to have an effective range of less than 

 44 feet. Apart from this set of traps, which cannot be used for purposes 

 of comparison, the sets of 12, 8 and 6 were distinctly more effective than 

 the sets of 4 and 3, and the set of 6 had an effect intermediate between 

 those of 12 and 8. In another experiment 3 and 6 traps were exposed 



Ann. Biol, vii 7 



