A new technique for monitoring Trigona carbonaria nest contents, brood and activity using X-ray computerized tomography

Brood status in the Australian stingless bee Trigona carbonaria is difficult to monitor non-invasively as splitting the hive damages the nest, and the involucrum prevents observations of internal structures and evidence of queen activity. In addition, increases in hive weight, also used as a measure of colony health, can be attributed to increased pollen and nectar collection by foragers in times of colony stress rather than improved brood status. To assess brood status and queen activity, we performed helical two-dimensional and three-dimensional X-ray computerized tomography (CT) to measure brood chamber volume in a T. carbonaria hive. All previously reported nest structures including larval cells, pupal cocoons, involucrum, cerumen and batumen layers were clearly identifiable. In addition, the on-screen linear callipers enabled accurate estimates of brood chamber volume to be made. A batumen bridge was found that may secure the brood chamber to the base of the hive box; this structure has not been reported before. CT could be used to follow the life cycle of stingless bees, track the development of natural nests and observe nest morphology to distinguish between species of Trigona. In addition, sequential scans will be useful in non-invasively assessing changes in brood status.