A look at the research into termite queens, their lifespans and reproductive behaviours.
Many pest managers will understand the basics of termite colony founding. Male and female termites pair off after a nuptial flight and move off together to find a suitable site to found the nest. The female – the queen termite – is seen as the most important termite in the colony and is often referred to as an ‘egg- laying machine’. The success of the colony is dependent on the survival of the queen, but the death of the founding queen does not necessarily mean the death of the colony.
Termite reproductives can be long lived. Kings and queens of Mastotermes darwiniensis laboratory colonies have been reported as living for over 20 years.1 A (very!) long-term study looking at the drywood termite, Cryptotermes secundus, monitored the survival of termite queens over their entire lifespan.2 Using field-collected, newly established colonies, a group of researchers maintained the colonies under laboratory conditions for 15 years. Under these controlled conditions, the average lifespan of the queens was 13 years.
What was particularly interesting was that the queens were not subject to a gradual ageing process. Instead they demonstrated a physiological upheaval at old age, characterised by stress and sudden death. So how does a termite colony survive when the queen dies?
Subterranean termite queens are capable of producing secondary neotenic reproductives that can maintain colony productivity after the original queen has died. There is an increasing body of work that shows that these secondary queens are produced by parthenogenetic (asexual) reproduction, whereas the workers and alates are produced through normal sexual reproduction.
One group of researchers collected and analysed 30 field colonies of Reticulitermes speratus.3 They found that in all but one of the colonies, the primary queen had been replaced by numerous secondary queens. But even in the colony where the primary queen survived, some 120 secondary queens were present. In contrast, all but two colonies had a single primary king, with the other two having a single secondary king.
Genetic analysis showed that the secondary queens were genetically identical, and didn’t have genes from the king, indicating that they were produced asexually. By contrast, 100% of the workers and 95% of the alate nymphs had genes from both the king and queen, indicating they were produced by sexual reproduction.
This reproductive strategy for producing secondary queens has been dubbed ‘asexual queen succession’. By producing secondary queens genetically identical to herself, the original queen maximises the colony output and retains the transfer of her genes to the next generation, even after she dies and has been replaced. These secondary reproductives mate with the founding king, which tends to outlive the founding queen.
Although the number of secondary reproductives varies between species, researchers believe the fact that this combined strategy of asexual and sexual reproduction has now been recorded in a number of evolutionary distant species of termite (Rhinotermitidae, Termitinae and Syntermitinae), highlights that there are significant advantages in this reproductive strategy. The historical view of a lifelong monogamy between a primary queen and king in termites now appears obsolete.4
1 Thorne, L.T et al. (2002). Longevity of kings and queens and first time of production of fertile progeny in dampwood termite (Isoptera; Termopsidae; Zootermopsis) colonies with different reproductive structures. Journal of Animal Ecology 71: 1030-1041.
2 Kuhn, J.M.M et al. (2020). Disentangling the ageing network of a termite queen. doi: https://doi.org/10.1101/2020.12.19.423576
3 Matsuura, K. et al. (2009). Queen succession through asexual reproduction in termites. Science 323: 1687
4 Hellemans, S. et al. (2019). Widespread occurrence of asexual reproduction in higher termites of the Termes group (Termitidae: Termitinae). BMC Evolutionary Biology 19: 131
More research on termite nests and reproduction.