Radio frequency identification (RFID) systems were initially developed for tagging and identifying stored goods. They are non-contact identification systems consisting of two components: (1) The transponder (tag), which is attached to the object that needs to be identified; (2) The reading device (scanner), which is required to retrieve the information stored on the transponder (Finkenzeller, 2002).
The tag is the data storage medium of the RFID system and usually has no on-board power supply, allowing maximum miniaturization. The energy needed to retrieve the information stored on the tag is provided by the scanner via inductive coupling. As soon as the tag enters the operating distance of the scanner it will be activated, enabling the transfer of the identity data to the scanner (Finkenzeller, 2002).
The majority of RFID tags consist of a spatially separated transponder coil (antenna) and transponder chip (hybrid technology; Finkenzeller, 2002). This design limits the level of miniaturization and their use in honey bee studies. A different tag design in which the antenna is planarly coiled on the surface of the chip (Coil-on-Chip; Jurisch, 2001; Finkenzeller, 2002) results in dimensions of 0.8 or 1.6 mm2 and weights of 2 or 4 mg. These devices are much more appropriate for use on honey bees. The technique was first used by Streit et al. (2003). Recently, Decourtye et al. (2011), Schneider et al. (2012), and Henry et al. (2012) determined effects of insecticides on foraging activity with RFID technologies.
The RFID equipment (tags, scanners, software) in the aforementioned studies was provided by microsensys GmbH, Erfurt, Germany. The tag belongs to the mic 3-series (mic 3-64) with a 64 bit read-only (RO) memory containing the ID-number. It works at a frequency of 13.56 MHz and the reading distance is limited to 2 – 4 mm (depending on the size of the tag). Different scanner models are available. Among these are the 2k6 HEAD used in the studies of Decourtye et al. (2011) and Schneider et al. (2012). A new scanner model has recently been released. To our knowledge, no studies have been published with this model yet.
A special characteristic of the 2k6 HEAD readers is their direction sensitivity. Two separate, cascaded reader-antennae provide the information on the movement direction of an RFID-tagged honey bee. This yields information about the time a given tagged bee spent outside or inside the colony. To retrieve data collected by the readers, they are equipped with a serial interface to establish a connection to a computer. A USB to serial adapter (e.g. ATEN USB to SERIAL ADAPTER, chipset PL 2303) can be used for the data transfer.