1. The survey of Diatraea spp. in their primitive habitats has been extended to cover the interior Guiana plateau, the Rio Branco, the lower Rio Negro and the lower Amazon.
2. The greatest practical result has been the discovery and introduction into British Guiana of the Amazon fly parasite (Metagonistylum minense) of D. saccharalis.
3. The most interesting ecological result was the finding of several Diatraea spp. as original members of a true savannah association.
4. The twelve species considered are grouped as forest, riparian, savannah and domestic species.
5. The two forest species are D. bellifactella and D. brunnescens.
6. Riparian grass associations are developed over huge areas on the lower Amazon, where they may be divided roughly into three main zones, dominated by Paspalum repens, Echinochloa polystachya and Paspalum fasciculatum, respectively.
7. The chief, and in fact only Diatraea of the first and second zones, is D. saccharalis, which is occasionally abundant.
8. The P. fasciculatum zone is colonised by D. amazonica and D. myersi.
9. The pure savannah species are D. canella, D. impersonatella, D. savannarum and D. cayennella.
10. D. lineolata is practically confined to maize, and no wild host-plants, either naturalised or indigenous, are known.
11. Five species attack cane, namely, saccharalis, busckella, impersonatella, canella and albicrinella, and all except the latter are major pests over considerable areas.