Laser marking of the carabid Pterostichus melanarius for mark-release-recapture.
Marking, releasing, and recapturing insects in traps are used widely to estimate dispersal distances, habitat preferences, and population density. The limiting factor in using this technique is often the difficulty of marking large numbers of individuals (Dent & Walton, 1997), especially when candidate species such as the beneficial predatory beetle Pterostichus melamarius (III.) may number 140 000 per hectare (Purvis & Fadl, 1996). Associated statistical procedures are well developed (Schwarz & Seber, 1999) but cannot compensate for low recapture rates.
Current marking techniques include paints, dyes, immunoglobulin, abraded and branded marks, radio isotopes, and rare earth elements, and have been reviewed by Southwood and Henderson (2000) and Hagler and Jackson (2001). Some of these methods are impermanent while others are potentially toxic, time consuming and difficult to apply (causing handling mortality). Techniques such as the use of immunoglobulin allow batch marking but do not provide unique codings to allow identification of individuals. This study introduces a rapid technique to mark insects individually with a unique identity number using a laser.