Seminar Thursday 18 th September 2003, at Department of Population Ecology
By
Wageningen University, The Netherlands
The termite Bulbitermes sarawakensis (Nasutitermitinae, Termitidae) lives in lowland tropical rainforests in Malaysia and Indonesia. The species lives in arboreal nests and moves in covered runways, ‘galleries’. As a Nasutitermitinae species, its soldiers possess a nasute which they use for chemical defence.
Because not much is known about caste biology of this species, a laboratory study focused at colony composition and a field study was done on caste behaviour and caste ratio in galleries.
Lab study We abscised one complete nest from a tree and made biometrical studies of its inhabitants. One queen, eggs, first and second stage larvae (making up 4.4% and 6.7% of the colony respectively), presoldiers (0.2%), soldiers (10.7%), a small and a big worker caste (39.0% and 37.4%), different stages of nymphs with long wings (0.5%) and two stages of nymphs with wing pads (1.2%) were found. The function of the latter is not understood.
Field study Part of a gallery was broken in order to see the termites. Only workers and soldiers were present in galleries and both were involved in defence behaviour after this disturbance. An increasing number of soldiers immediately swarmed out. This indicates that soldiers might be recruited to the place of danger. Subsequently they formed the border of the open space, with their nasutes pointed outwards. Workers first retreated in the gallery but gradually resumed walking across the open space. They contributed to defence by rebuilding the gallery.
When foraging activity had resumed, we measured activity (number of passing soldiers and workers per minute) and caste ratios (#workers : #soldiers). There was a positive exponential correlation between activity and caste ratio.
In general, the percentage of soldiers in galleries was twice as high as in the nest. This again indicates that soldiers are recruited to the more vulnerable places.
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