A review of the latest research on termite biology.
Latest termite biology research
With chemical communication integral to termite behaviour, it begs the question as to whether there are any differences in the antennae between the different termite castes. Researchers have recently characterised the antennae of alates, soldiers and workers in Coptotermes formosanus.1 They determined that the antennae of alates were longer than those in soldiers and workers, had more segments and twice as many antennal sensilla (sensory receptors). There was very little difference in the sensilla composition between males and females or between workers and soldiers. However, all termite castes had the same nine types of sensilla.
The researchers related variations in the abundance of the different sensilla types to the various behaviours of the castes. For example, workers had a sensilla mix that relates to their need to be more responsive to changes in humidity and temperature. They also noted that relative to body length, the soldiers had the longest antennae, which may help them perceive information from a relatively wider range, which could be beneficial in defence behaviours.
Also, alates had a great abundance of chemosensilla at the end of their antennae, which would make them more sensitive to environmental odours. This makes sense, as they need increased sensory awareness when in the open during the alate flight and pairing. However, it is interesting to note that antennal cropping, where the ends of the antennae are intentionally removed, has been recorded in dealates. The ends of the antennae are either self-cropped or removed by their partner. It is hypothesised that this behaviour reduces pheromonal sensitivity, which would align with the lower levels of sensitivity required in the enclosed nest environment rather than in the open.
Whilst many will be aware that pheromones are a key element of communication in termites, the involvement of geomagnetic fields in orientation and navigation is only just coming to light. Working with both Reticulitermes chinensis and Odontotermes formosanus, researchers have established that both species show a directional preference to the geomagnetic field under both light conditions and complete darkness.2 The researchers concluded that geomagnetic fields play an important role in termite orientation, especially when trail pheromones cannot provide a precise direction.
1 Castillo, Paula & Le, Nathan & Sun, Qian. (2021). Comparative Antennal Morphometry and Sensilla Organization in the Reproductive and Non- Reproductive Castes of the Formosan Subterranean Termite. Insects. 12. 576. 10.3390/insects12070576.
2 Gao, Yong & Wen, Ping & Cardé, Ring & Huan, Xu & Huang, Qiuying. (2021). In addition to cryptochrome 2, magnetic particles with olfactory co-receptor are important for magnetic orientation in termites. Communications Biology. 4. 1121. 10.1038/s42003-021-02661-6.