TWO NOTORIOUS INSECT PESTS. G95 



Thus, in this locality, the same teak trees are not, as a rule, defoliated 

 more than twice in any one year. This, however, of course depends on 

 the local conditions of climate, &c. From the above it is clear that the 

 development of a large number of larvae in any one generation, in places 

 where the food supply is limited, is prejudicial to the development of 

 a large number of individuals in the immediately succeeding generation. 



60. So far as Pyrausia is concerned, the larval attacks are certainly 

 more severe in pure teak forests than in mixed forests. 



61. In the case of Ifyhlcea it has been shown above that the 

 natural food plant of the larva is apparently not teak, but plants belong- 

 ing to Bignom'acece, also that the larvae find some difficulty in adapting 

 themselves to a teak-leaf diet, and that the larval development is, at first 

 at all events, if not later, slower on teak leaves than on the leaves of 

 Millingtonia hortensis for example. Generally speaking, then, mixed 

 forests, containing a large proportion of plants belonging to Bignoni- 

 acece, would be more favourable to the development of the insect than 

 pure teak forests would be. In the former, also, a certain number of 

 larvae would be kept alive on food which suits them best, in years 

 which are unfavourable to the development of the insect on a large scale. 



62. Of course in years when the insect is present in large numbers 

 and the favourite larval food runs short in consequence, teak, in common 

 with several other species, is attacked, and once the insect becomes 

 established in a pure teak forest, the number of teak which suffer will of 

 course be far greater than would be the case in a mixed forest. 



ENEMIES. 



A. P. machoeralis — 



63. The larvae suffer from the attacks of an ichneumon and also 

 from what appears to be a fungoid disease. Leaf spiders also attack and 

 kill the larvae. Bulbuls are said to eat the larvae, and I have often 

 found large numbers of these birds in an attacked forest. 



B. II. puera — 



64. The larva is a voracious feeder, but the insect has, fortunately 

 for the forest, some powerful enemies which account for its generally 

 occurring in fewer numbers than the Pyrausta. It is very liable to a 

 disease apparently caused by a fungus. The larva is usually attacked, 

 but I have also found pupae killed by it. The diseased larvae and pupae 

 become discoloured, wet and flabby, being filled with a yellowish-brown 

 liquid. 



