Spatial and temporal distribution of rhinoceros beetles Oryctes Hellwig (Col.: Scarabaeidae) in date palm plantations of Khuzestan province

The activity of Oryctes Hellwig(Coleoptera: Scarabaeidae)causes severe damage to date palm. In order to study spatial distribution, 23 date palm plantations as sampling areas were selected. Geostatistical methods were used to simulate spatial distribution models. Correlation and overlap indices of ecological niches were calculated. To investigate the temporal distribution, a plantation was randomly selected in Abadan, Shadegan and Behbahan areas and sampling was performed biweekly intervals. Time series models were used to study seasonal population fluctuations. The results showed that spatial distribution of the rhinoceros beetles, O. elegans and O. agamemnon were compatible with spherical and linear models, respectively. The effect of the fragment was approximately the same, at about 9.7-9.9 and variograms ranged from 3.8 to 3.2. According to the results, the relative probability (Oij) of O. elegans in 87.5% of sampling points was higher than O. agamemnon. The overlap of ecological niches of the two species (D) ranged from 0.94 to 1. Populations of the two species started their activity from late February to early March. Population growth for both species continued in spring and early summer. Population growth rate for O. elegans was more than O. agamemnon. The maximum population densities of O. elegans and O. agamemnon were calculated in June and July with a time difference of about one month in the two regions of Abadan and Shadegan, respectively. In Behbehan area, the peak population density for O. elegans and O. agamemnon was almost identical, in the second week of June. The results of this study could be used for control monitoring, designing an integrated management program and assessment on the risk of rhinoceros beetles.