Third-stage larvae of the following species of Dynastidae associated with coconut palms are described: Xylotrupes gideon (L.) (including four subspecies, X. g. ulysses (Guérin), X. g. szekessyi Endrődi, X. g. beckeri Schaufuss and X. g. asperulus Minck), Scapanes australis (Boisduval) (including three subspecies, S. a. grossepunctatus Sternberg, S. a. salomonensis Sternberg and S. a. australis (Boisduval)), Trichogomphus fairmairei Arrow, Oryctes rhinoceros (L.), O. centaurus Sternberg, Oryctoderus latitarsis Boisduval and Oryctoderus sp. (either O. coronatus Bates or O. godeffroyi (Fairmaire). A key to species, based on larval characters, is included. Some small differences, particularly in setation, were found among the four subspecies of X. gideon examined, and differences in setation of the abdominal segments were found between S. a. grossepunctatus and S. a. salomonesis on the one hand, and S. a. australis on the other.