84 Habits of the Tomato Moth 



4. ORIGIN AND METHOD OF DISPERSAL. 



There are three ways in which the pest may be introduced. Firstly, 

 seedlings carrying the eggs or young larvae may be purchased from an 

 infested nursery. Secondly, market baskets may bring in the pupae. 

 Cases of both these are known, and they are sufficient to account for 

 its appearance in new localities, supposing that it originated in only 

 one place. Thirdly, the moth itself may enter through broken panes 

 or open ventilators. 



An experiment was carried out to discover to what extent this moth 

 does enter the greenhouses. A block of seven 200-foot houses which 

 had been used for propagating two lots of seedlings, was finally planted 

 out the first week in May. The two houses at the east end of the block 

 were isolated from the others by means of a sheet of hessian, and were 

 made moth proof. Porches of hessian, with tightly fitting second doors, 

 were built over the entrances at one end, while the doors at the other 

 end were nailed up and caulked. The building was overhauled and put 

 in perfect repair. The roof ventilators were screened with tinned steel 

 woven wire, the mesh of which was one-sixth of an inch square. The 

 large ventilators over the doors were replaced by cones of the wire 

 mesh, which were directed downwards into the houses, and ended in 

 sleeves of calico to which were attached glass jars half filled with water. 

 In screening the roof ventilators it was necessary to arrange the wire 

 in the form of bags in which the gear could work freely. In one of the 

 houses these bags were completely closed, and in the other, one end of 

 each opened into a calico sleeve which dropped into the interior of the 

 house and opened into a glass jar of water. The sleeves were 18 ins. 

 long, 6 ins. in diameter at the top, and 3 ins. at the bottom. This 

 arrangement was devised under the impression, then generally held, that 

 the moths invaded the houses in large numbers. The writer was informed 

 that sometimes four or five were found jammed in the cracks around 

 a door and agreed with the natural conclusion that they were trying 

 to force their way in. The jars were arranged to trap moths deliberately 

 trying to enter the houses, as it was thought that in trying to reach the 

 plants below they would pass down the sleeves and be caught in the 

 water. It is now known that the moths caught in the cracks were 

 endeavouring to force their way out, and the experiment from this 

 point of view was badly devised. The screening was not completed till 

 June 14 owing to the difficulty of obtaining material (see PI. IX, fig. 3). 



A female H. oleracea was found in one of the jar traps on July 30, 



