76 Habits of the Tomato Moth 



also considerable variation in this respect among different batches, and 

 among the individual members of a particular batch. The same pheno- 

 menon has been met with rarely in larvae confined to a diet of Cheno- 

 jpodium, since occasionally one apparently starved though food was 

 abundant, and conditions healthy. It is of interest that the only other 

 case when an attempt at breeding from the egg failed entirely was on 

 another Solanaceous plant, S. dulcamara. This suggests that the heavy 

 death rate on tomato may be due to one or other of the poisons which 

 are characteristic of this group of plants, and to which the majority 

 of the larvae may be not immune. On the other hand the recoveries of 

 the larvae which were transferred from tomato to Polygonum recall 

 strongly the recoveries of beri-beri patients when they are supplied with 

 a diet containing the vitamines deficient in their former food. The large 

 death rate may be due to a deficiency in tomato foliage of some substance 

 essential to the maturing of the larvae. 



Whatever the cause of this phenomenon it adequately explains why 

 the larvae, though surrounded by abundant tomato foliage in the glass- 

 houses, often leave it and feed on the hard green fruits, and bite into the 

 stems and eat along the pith, in their search for a more suitable diet (see 

 PI. VIII, figs. 1 and 2). It explains also why the tomato crop in the heavily 

 infested nurseries has not been entirely destroyed. As will be shown 

 presently there are two complete generations and a partial third in the 

 tomato houses in the season, and the offspring of a single pair of moths, 

 emerging in April, might be nearly half-a-million caterpillars in the 

 second generation in August, if all survived ; or an average of 30 to each 

 plant over an acre. Such numbers have of course never been attained 

 in any nursery, and as the moths emerge by the hundred to an acre in 

 the heavily infested houses in the Spring, the death rate of the larvae 

 during growth must be enormous. Apparently the young ones scatter 

 in very large numbers from the tomato plants in searching for more 

 suitable food and most of them fail to regain the plants. 



The larvae have been successfully reared on Polygonum in a cucumber 

 house, but two attempts to rear them from the egg on cucumber foliage 

 failed. In one of these cases 14 larvae from a batch of about 100 eggs 

 passed the first moult and lived eight days, but none survived the second 

 moult and they were all dead on the 11th day. Twenty half -grown 

 larvae which had been collected from tomato plants were fed on 

 cucumber foliage. One of these became a small healthy pupa on the 

 22nd day after commencing the cucumber diet, two others were then 

 alive but died on the 28th and 29th days respectively, apparently of 



