Ecological methods for adult populations of Oryctes rhinoceros (Coleoptera, Scarabaeidae)

Abstract

ABSTRACT. 1. For comparing assessment methods, O.rhinoceros (L.) populations were monitored in five 30–50 ha plots in southern Luzon, Philippines. No consistent correlations were found between number of beetles caught in traps, amount of palm damage and number of breeding sites. Apparently, plots were too small to account for fast dispersal of beetles.2. Coconut cap traps baited with ethylchrysanthemumate attracted O.rhinoceros adults searching for breeding sites. Several factors were identified influencing catches but trapping was found to be unsuitable for accurately assessing pest populations.3. A new method which gives estimates on the monthly number of O.rhinoceros attacks on coconut palms, was tested in the Maldives. Palms are climbed about once a year and the sequence of fronds, the number and the position of beetle cuts are recorded.4. Reduction with age of the length of three teeth on the fore tibia of O. rhinoceros adults was studied in the Philippines. The data was insufficient to obtain a clear correlation between age and length of teeth.5. The observations indicated that in the Philippines after leaving their site of pupation, O.rhinoceros adults spend about 5 weeks feeding on coconut palms. This is followed by a period of about 7 weeks in breeding sites and, on occasion, additional visits to palms. With these estimates it was possible to relate palm damage records with numbers of feeding adults.