Retention of external and internal markers by Southern pine beetles (Coleoptera: Scolytidae) during gallery construction

If retained, markers used in mark-release-recapture studies of bark beetle dispersal could provide valuable tools in the determination of post-dispersal fate. Retention of the internal marker rubidium (Rb) and of the external marker fluorescent powder during egg gallery construction, oviposition, and feeding were quantified at intervals from 0 to 96 h by allowing marked Southern pine beetles, Dendroctonus frontalis Zimmermann, to carry out these activities in untreated host material. Significant differences in Rb concentrations were found between fed and unfed Rb-marked beetles at all intervals after 12 h. Unfed Rb-marked beetles were detectable at all intervals, whereas reliable detection of fed Rb-marked beetles declined with time. Over 90% of fed southern pine beetle marked with fluorescent powder were detectably marked after 96 h, while less than 50% of the Rb-marked beetles were detectable after 72 h. Neither marking technique adversely affected the gallery length or number of eggs produced by marked beetles compared to unmarked beetles allowed to excavate for 96 h. Practical aspects of both techniques are considered.