Question Monogamy in Termites

Title: Scientists solve the mystery of why termite kings and queens are monogamous
Published by: The University of Sydney
Published: 30th of January, 2026

From the Article: 
New research from the University of Sydney has uncovered a surprising answer: termites didn’t become more socially complex by gaining new genes, but by losing them – including genes linked to sperm competition. The findings shed new light on the long-standing question of whether monogamy is essential for the evolution of complex insect societies.

The international study, published in  Science , traces termite evolution back to ordinary cockroaches – including the ancestors of modern ’domestic’ cockroaches – that began feeding on dead wood. This dietary shift triggered a cascade of genetic and social changes that eventually produced termites and their highly organised colonies.

One of the most striking discoveries was that termite and woodroach genomes are smaller and simpler than those of cockroaches. 

“The surprising result is that termites increased their social complexity by losing genetic complexity,” Professor Lo said. “That goes against a common assumption that more complex animal societies require more complex genomes.

'The most telling losses were genes involved in building the tail, or flagellum, of sperm. Unlike cockroaches and most animals, termite sperm lack tails and are immotile.“This loss doesn’t cause monogamy,” Professor Lo said. “Instead, it’s a strong indicator that monogamy had already evolved.”In most animals, including cockroaches, females mate with multiple males. This creates intense sperm competition, favouring fast-swimming sperm with tails. But once termite ancestors became monogamous, sperm competition disappeared – and sperm tails were no longer necessary.'

This finding feeds directly into a long-running scientific debate about whether close genetic relatedness is required for complex social systems to evolve. Some researchers have argued that high relatedness is not essential. This study suggests that, at least in termites, monogamy and high relatedness were crucial.

The research also explains how termite societies are organised from within. Experiments showed that whether a young termite becomes a worker or a future king or queen depends heavily on nutrition during early development.

Larvae that receive abundant food from older siblings develop high energy metabolism and become workers, who don’t reproduce. Those that receive less food grow slowly at first and retain the potential to become reproductives later in life, that is kings or queens.

 When a termite king or queen dies, monogamy does not end. Instead, the role is usually filled by one of their own offspring, leading to widespread inbreeding within colonies.“From an evolutionary perspective, that reinforces relatedness even further,” said Professor Lo, who is part of a dynamic and growing insect research group in the School of Life and Environmental Sciences at the University of Sydney.By combining genomics, physiology and behaviour, the study offers one of the most comprehensive explanations yet for how termites made the leap from solitary cockroach ancestors to some of the most socially complex organisms on the planet.“This work shows that understanding social evolution isn’t just about adding new traits,” Professor Lo said. “Sometimes, it’s about what evolution chooses to let go.”

Read More Here: 
Cui, Y. et al ‘Nutritional specialisation and social evolution in woodroaches and termites’ ( Science  2026) DOI: 10.1126/science.adt2178

www.sydney.edu.au/news-opinion/news/2026/01/30/termite-evolution-nutrition-specialisation-insect-monogamy.html