In Papua New Guinea, Coleoptera associated with coconuts share or have similar larval breeding sites, which has led to some confusion with their identity. Conclusive identification of these larvae is important before deciding whether it is possible to use biological control measures against them. The available keys are complex and do not take into account simple observable characters that can be used in the field with live specimens. Specimens of the following species were examined: Xylotrupes gideon (L.), Trichogomphus vicinus Dechambre, Oryctoderus latitarsis Boisduval, Oryctes centaurus Sternberg, Oryctes rhinoceros (L.), Scapanes australis Boisduval (Coleoptera, Scarabaeidae, Dynastinae), Dermolepida sp. (Coleoptera, Scarabaeidae, Melolonthinae), Cetoniinae (Coleoptera, Scarabaeidae) and Lucanidae (Coleoptera Scarabaeoidea). A simple key to distinguish 2 important pest species, O. rhinoceros and S. australis, from allied Coleoptera directly in the field is presented, together with drawings and photographs to illustrate distinctive features to assist in using the key. The identifications presented in the paper were checked against existing taxonomic keys.