I am planning on conducting an insect-tracking experiment in the field. We are going to have square enclosures (15m x 15m), where our insects can move around freely, but will not leave the enclosure. We want to track each individual (around 50 individuals per enclosure) throughout the summer season. I was considering PIT (Passive Integrated Transponder) tags glued on individuals, as it has been previously successfully applied to small size insects; however the reading range is way too short for our experiment (0.5 meters). I understand (hopefully correctly) that the same problem applies to passive RFID systems: impressively small tags, but range of readers too weak.
What would be your suggestion to achieve this reading range (15m x 15m), without making any sacrifice from the small-size of the tags?
For my experiment, the optimum size of tags would be smaller than 1 cm.
I apologize in advance for my lack of electrical engineering knowledge - it would have been a more informative question if I knew exactly what I'm dealing with and used the right jargon.