Microdot technology for individual marking of small arthropods

Individual mark-release-recapture is an important method for gathering data on insect movement, although it is limited by the constraints of tagging small insects with individual information. Microdots, originally developed for covert security applications, are small polymer discs (diameter 0.5 mm) bearing up to 26 characters of information and have the potential as an alternative to the larger bee tags. In the present study, we test microdots for the individual marking of a 9-mm parasitoid wasp. We individually marked 505 wasps. The recapture rate was 24% of individuals over 189 recapture events, for which 84% retained legible microdot labels. Movement was in the range 0-161 m with a mean displacement 21.2 ± 2.7 m. A captive survival experiment showed no difference in lifespan between marked and unmarked wasps. The present study shows that microdots can provide an effective, durable, low-cost method for individually tagging small insects. The technique offers new opportunities by greatly expanding the capability for individually marking small insects, shifting the minimum size below that of bee tags, which is the only other manufactured option for individualized miniature marking.