Differences of morphology of antennae between soldiers and workers in Coptotermes formosanus (Isoptera: Rhinotermitidae)

The antennal sensilla of insects function at the site for the reception of stimulants and the transduction of information. The types and distribution of antennal sensilla of soldiers and workers in Coptotermes formosanus Shiraki were investigated using photomicrography and scanning electron microscopy in this study. The results showed that there were 6 types of sensilla on the antenna of soldiers and workers in Coptotermes formosanus: sensilla trichodea, sensilla chaetica, sensilla basiconica, sensilla placodea, sensilla campaniformia, and sensilla mammilla. Moreover, a great number of sensilla placodea, sensilla campaniformia and sensilla mammilla were found on the joint between segments. The length of the joint was the longest in the middle of antennae and the shortest near the end of antennae. Behavior bioassay results indicated that the soldiers could discriminate non-nestmates when their antennae were kept >= 8 segments. These suggest that the chemosensory sensilla functioning as nestmate recognition are located on the 8(th)-15(th) segments of the antennae in C. formosanus. Thus the joint between antennal segments might be the key position in receiving and processing signals in the nestmate recognition, which may be mediated by the sensilla placodea, sensilla campaniformia and sensilla mammilla in the C. formosanus.