DESIGN OF AN INSTRUMENTED SANDPIT TO MONITOR SUBTERRANEAN TERMITE AND ANT ACTIVITY IN VIBRATION BIOASSAYS

Termites are known to use vibrational communication in the form of alarm, walking and feeding signals, for the survival of the nest against predators and competitors, as well as unfavourable microclimate conditions. However, less is known about the mechanism of sensing and dispersion of this information as most termite species are cryptic, hiding their presence through quiet and remote interactions with their environment. To study how vibration communication is facilitated in subterranean termite species such as Coptotermes acinaciformis, we designed an instrumented sandpit to monitor their behaviour in making foraging decisions, and in response to threats from a major predator such as the ant Iridomyrmex purpureus. The sandpit enclosure design simulates conditions typically found in and around termite nests - moist sand maintained at a constant temperature and relative humidity, and with dry/wet wood samples of different shapes and sizes. The enclosure has a modular design with transparent side walls to enhance visibility for video tracking of tunnelling activity in sand or termite soil and can be interchanged for mounting various sensors and wood pieces. The planned bioassays incorporate both passive and active control mechanisms to manipulate termite behaviour. To capture vibrations generated at the source and propagating through the substrate and sand (or soil) medium, we use vibration sensors such as accelerometers and geophones placed at defined distances around the termite nest. We also implement a continuous environmental monitoring system by embedding highly sensitive optical fibres measuring strain, temperature and humidity in the enclosure. We have validated the sandpit enclosure by vibration and modal tests, and finite element analysis after a model updating procedure, allowing the design of bioassays in a virtual environment before conducting controlled experiments in the laboratory. This system can also support the development of bio-informed sensing and actuation mechanisms for soft robotics and structural health monitoring applications.